Buffy the Vampire Slayer (Riff Regan vs. Alyson Hannigan)

What they changed: Joss Whedon financed the original pilot himself, formatting it as a half-hour episode. It is, for the most part, a shortened version of "Welcome to the Hellmouth," but with different casting. The role of the Sunnydale library was played by Torrance High School's library — a much larger and airier room than the cramped Hellmouth library we've come to know and love, with a handy second floor for showing off those Buffy backflips. Instead of Ken "Hyena Chow" Lerner as Principal Flutie, we get a much more straightlaced interpretation from character actor Stephen Tobolowsky. But perhaps the biggest difference is in the role of Willow. Instead of Alyson Hannigan, the geeky witch was originally played by Riff Regan.

How might the series have been different? Flutie probably would have still ended up in the stomachs of his students, but the Scooby Gang might have never been the same. Regan's Willow was a sweet doormat, but she didn't have quite the neurotic, eager-to-please quality Hannigan brought to the role. Incidentally, it wasn't the first time Hannigan replaced an actress after the filming of a show's initial pilot. In 1989, she took over the role of Jessie Harper in the fantasy sitcom Free Spirit.

Unaired Pilot with Stephen Tobolowsky and Riff Regan:

Official Pilot — "Welcome to the Hellmouth:"

Dollhouse (Joss Whedon vs. Fox)

What they changed: The premise and the characters are the same, but the stories unfold in a rather different way. We're initially introduced to Echo through a trio of very different engagements: one philanthropic, one as a revenge date, and one where she talks down gangsters in Espagnol. Boyd is already Echo's handler, and Topher has already caught onto Echo's bison-like grouping with Victor and Sierra. Agent Paul Ballard also comes face-to-face with Echo in the original pilot...when Topher programs Echo to kill him.

How might the series have been different? The original pilot played more as the start of a noir series than as a proof-of-concept for an engagement-of-the-week serial (which is what the official pilot "Ghost" suggests). We probably would have leaped to Dollhouse's underlying plot more quickly, and spent more of the season focusing on Echo's emerging awareness. Plus, it seems the Dollhouse was originally going to be more hands on in addressing Ballard's investigation. We see some of that noir (and slightly more classically Whedonesque dialogue) in the original pilot clip below:

Terminator: The Sarah Connor Chronicles (Bad-Ass Sarah vs. Vulnerable Sarah

What they changed: The most readily obvious difference between the unaired pilot and what aired on Fox is that Tim Guinee, who played Tomin in Stargate SG-1, was originally cast as Sarah's jilted fiance Charley, but was replaced in the official pilot by Dean Winters. But more significant is a key change in the final scene. In official pilot, when Sarah Connor delivers her final voiceover, we see her caress her son's face before walking into her home. In the original pilot, we instead see her pulling a gun out of its hiding place while Cameron and John sit in the same room preparing their weapons, showing that Sarah's focus is on the coming war.

How might the series have been different? It's hard to say to what extent this change represents a shift in tone across the series, but we worried that it signaled a "wimpifying" of Sarah Connor, showing her vulnerability where it could have shown her strength and determination. You can scene the unaired scenes and their official pilot counterparts below:

Life on Mars (US) (Sunny LA vs. Gritty NY)

What they changed: Pretty much whatever they could. The original pilot for the US adaptation of Life on Mars was thoroughly panned, and producers quickly moved the action from Los Angeles to New York (allowing for that Twin Towers shot), and recast several roles. Star Trek vet Colm Meaney was replaced by Harvey Keitel in the role of Gene Hunt and Gretchen Mol took over Rachelle Lefevre's role as Annie Norris (Lefevre might have experienced an unfortunate moment of deja vu when she was recently replaced in yet another role — as the vampire VIctoria in Eclipse). But beyond that, certain scenes from the original pilot were rewritten to more closely match the UK version, and made the scenes visually darker and more textured.

How might the series have been different? It simply wouldn't have been as good. The original US pilot genericized the UK version, washing it of all character. By ultimately sticking closer to the source material, the US version of Life on Mars was able to echo its tone while creating a new mythology to explain Sam Tyler's predicament.

Scene from the Unaired Pilot:

Scene from the Official Pilot:

Star Trek (Christopher Pike vs. James T. Kirk)

What they changed: The original pilot "The Cage" was a completely episode from the official Star Trek pilot "Where No Man Has Gone Before," with an almost completely different Enterprise crew. In lieu of William Shatner's syncopated Captain Kirk, Jeffrey Hunter was set to helm the ship as Captain Christopher Pike, and Star Trek creator Gene Roddenberry's future wife, Majel Barrett, played his intellectual and rational second-in-command, known only as "Number One." Spock would be the sole crew member to make the transition from first pilot to official pilot, but even he would undergo some minor changes. The original pilot's Spock was known to smile and use human colloquialisms, while the final Spock inherited Number One's sense of cold, hard logic.

How might the series have been different? The basics of the Enterprise and the Federation would have remained largely the same (in fact, most of the footage from "The Cage" would be cannibalized for a later episode "The Menagerie"). But the dynamics of the crew would have been very different. Pike wasn't the emotive adventurer Kirk would be, and he wasn't cast in as nearly sharp relief against either Spock or Number One. Plus, the original pilot's entirely caucasian cast was hardly the rainbow coalition that made the final version of Star Trek such a progressive piece of television.

Original Pilot — "The Cage:"

Official Pilot — "Where No Man Has Gone Before:"

Doctor Who (The Doctor from the 49th Century vs. The Doctor from Another Time

What they changed: The original episode of the first Doctor Who serial "An Unearthly Child" has the feel of a filmed dress rehearsal, but there were a few changes made beyond tightening the performances and improving production values. The Doctor and Susan both undergo costume changes — Susan into a more casual, less futuristic look and the Doctor from a modern suit to an Edwardian one — and the Doctor is much less gruff than in the original pilot. Also, in the original pilot, the Doctor and Susan talk specifically about being from the 49th Century, rather than the being from "another time, another world."

How might the series have been different? Aside from making the First Doctor outright hostile to his new companions instead of largely indifferent to them, the original pilot is a bit less mysterious about the Doctor and Susan's origins. If it had gone to air, it might have set the stage for a Doctor who is less coy and more forthcoming.

Segment from the Original Version:

Segment from the Official Version:

Stick Around: Before landing on Taxi, Andy Kaufman shot a pilot for this futuristic sitcom. Doing a version of the "Foreign Man" schtick that would make Taxi's Latka so popular, Kaufman played Andy, an oft-malfunctioning android servant for a couple living in 2055. Vance Keefer, Andy's owner, owned an antiques shop, but was often misinformed as to the original uses of his inventory.

Red Dwarf USA: Long before the US moved The Office to Scranton, Pennsylvania, Universal Studios tried remake the hit science fiction comedy Red Dwarf for American audiences. Two pilots were shot for the US version, with different actors in the roles of Cat and Rimmer (the second pilot even pulled a gender switch on Cat, casting Terry "Jadzia Dax" Farrell in lieu of the first US pilot's Hinton Battle), but Robert Llewellyn reprised the role of Kryten in both pilots. Despite the recasting and refilming, executives were never quite pleased with the US version, and neither pilot ever aired in the US or UK.

Babylon Fields: When the dead rise from the grave in New Jersey, the don't start randomly chomping on the brains of their former friends and family members. They just want to go back to their lives — their families, their old jobs — and pick up right where they left off. The pilot episode indicated the series would be part zombie comedy (complete with a rigor mortis sex joke) and part procedural drama, with zombies seeking the help of law enforcement to solve their own murders.

Heat Vision and Jack: Ben Stiller directed the pilot episode of this send-up of the scifi action genre. Jack Black played Jack Austin, a former astronaut who became hyperintelligent after being exposed to extreme levels of solar energy. When his unemployed roommate Doug (Owen Wilson) gets zapped with a ray and merges with his motorcycle, the two team up to evade the evil forces of NASA. In a nod to his villainous roles, Ron Silver plays the NASA employee hunting down the duo — a character who just happens to be a sometimes actor named Ron Silver. The team tried to sell the series to Fox, but to no avail.

Area 57: Paul Reubens, Matthew Lillard, and Jane Lynch were signed as the on-screen comedy team for a Roswell-themed sitcom. Lillard was set to play Colonel Steven Isaacs, who had just joined a top-secret mission that involves observing a passive-aggressive alien (with some messy bodily fluids) played by Reubens. We never got to see what particular torments the captive ET had planned, since NBC failed to order the pilot.

Poochinski: Part reincarnation fantasy, part buddy cop comedy Poochinski is a bizarre chapter from the annals of poorly executed animatronics. Peter Boyle was somehow roped into this ill-conceived pilot about a murdered cop whose consciousness is somehow transferred to a bulldog. Naturally, he convinces his ex-partner to team up with him to bring his own killer to justice.

Gay Robot: Adam Sandler's bit about a sexually frustrated male robot who is attracted to human men made it into a full-fledged pilot. Comedy Central filmed the pilot in 2006 but never picked up the series, which is just as well since it felt like a Saturday Night Live sketch gone too long.

The Remnants: During the Writers' Strike, screenwriter John August teamed up with the likes of Ernie Hudson and Ze Frank to film a pilot for a possible web comedy, about a group of post-apocalyptic survivors who break into suburban houses and raid their fridges for non-perishable foods, while avoiding the human-looking monsters that lurk the streets. Ultimately, August says, they had trouble figuring out the business model, so a full series never emerged.

Where's Everett?: This proposed 1966 sitcom involved an alien ship landing in a quiet suburb and leaving an invisible baby in a basket on the doorstep of a kind-hearted human couple. The antics of an invisible infant probably sounded like a good idea until the writing staff had to come up with a second episode, but the project did have at least one feather in its cap: casting a pre-M*A*S*H Alan Alda as the adoptive father.

LAX 2194: Matthew Perry never would have been in Friends if the 1994 pilot for LAX 2194 had been picked up. The series would have starred Perry and The Drew Carey Show's Ryan Stiles as baggage handlers at a futuristic LAX Airport. In interviews, Perry seems generally relieved that he ended up sipping coffee in New York instead of handling alien suitcases in Los Angeles.

Starship Regulars: Starship Regulars was one of the early hits of online television, following the misadventures of a group of redshirts aboard a starship. Featuring the voices of Diedrich Bader and Michael Dorn, the original Flash cartoon series proved enough of a hit on Icebox.com that it was purchased by Showtime. Showtime looked into adapting the series as a full-length, live-action show, but sadly it never came to fruition.

The Adventures of Superpup (1958): The Superman TV series was such a hit that television producer Whitney Ellsworth tried to recreate the show with canine characters. The live action pilot featured little person actors in dog costumes. Reporter Bark Bent worked for Perry Bite with the Pamela Poodle at the Daily Bugle. But when danger strikes, Bent becomes Superpup. Reportedly, any humor in the pilot was completely unintentional, and the networks didn’t pick up the show.

The Adventures of Superboy (1961): Ellsworth made a second go of it in 1961, after the death of George Reeves made a planned revival of The Adventures of Superman unlikely. Like the Superboy comic, it was to follow the life of teenaged Clark Kent, his parents, and his suspicious friend Lana Lang. Ellsworth and Vernon Clark wrote 13 episodes, but only the pilot (available online) was ever produced. The next time Superboy would come to the small screen was five years later in a series of animated shorts.

The Thor Television Series (1988): In the 1988 TV movie “The Incredible Hulk Returns,” Bruce Banner learned that his former student, Donald Blake, had a mystical bond with Thor. The movie was meant to serve as a backdoor pilot for a Thor television series (with Steve Levitt as Blake and Erica Allan Kramer as Thor), but the series never went into production. Marvel may have had a similar idea for Daredevil with the follow-up movie, “The Trial of the Incredible Hulk.”

X-Men: Pride of the X-Men (1988): Before X-Men: The Animated Series, Marvel tried its hand at another X-Men cartoon. Fourteen year old Kitty Pryde joins the ranks of the X-Men (here Charles Xavier, Cyclops, Storm, Nightcrawler, Colossus, an Australian-accented Wolverine, and Dazzler) and battles the Brotherhood of Mutant Terrorists (Magneto, Toad, the Blob, Pyro, Juggernaut, and the White Queen). It was animated by Toei, the same company that did GI Joe and Transformers, but the dialogue is a bit on the atrocious side.

Generation X (1996): After a few years of success with the X-Men cartoon series, Fox decided to roll the dice on a live-action show. The made-for-TV movie/backdoor pilot Generation X takes place at Xavier’s School for Gifted Youngsters when Banshee and Emma Frost are at the helm. They recruit Jubilee (played by the very white Heather McComb) and deal with the amoral professor Russell Tresh. The show was never picked up, probably because of scenes like this one:

The Justice League of America (1997): CBS produced a pilot for a live-action JLA show to compete with Superman series Lois and Clark. It follows Tori “Ice” Olafsdotter as she is indicted into the League. Unfortunately, silly puns, sillier costumes, and poor production values ensured that the series never took flight.

Nick Fury: Agent of S.H.I.E.L.D. (1998): After nine years of Baywatch David Hasslehoff decided to return to his terrestrial action roots as Nick Fury. As with Generation X, Fox had the movie on a shoestring budget to see if anyone was interested in a series around the Hoff’s Fury. Apparently, no one was.

Bruce Wayne (1999): Before developing Smallville, Tobbins/Robbins Productions started work on a series about Bruce Wayne’s pre-Batman years. It would start when the orphaned billionaire was 17, and follow his travels to China, Korea, and France to go from spoiled playboy to crime fighting machine. Other characters would include comedian Jack Napier, psychology professor Jonathan Crane, hospital intern Harley Quinn, farm boy Clark Kent, police officer Jim Gordon, and mob boss Carmine Falcone. And Bruce’s best friend would be Harvey Dent, a bright young man with an abusive, alcoholic father. The project was shelved when rumors emerged that Frank Miller’s Batman: Year One was being adapted for the screen.

Global Frequency (2005): Survivor producer Mark Burnett turned Warren Ellis’ espionage comic into a TV pilot. Science fiction favorite Michelle Forbes (who played Ro Laren on Star Trek: The Next Generation and Helena Cain in Battlestar Galactica and is currently doing a turn on True Blood) was cast as Miranda Zero, the organizations head. The pilot was leaked online and was a bit of a hit, but Ellis claimed that the bigwigs at Warner were so annoyed by the leak that they killed the entire project.

The Amazing Screw-On Head (2006): As if you need further proof that Bryan Fuller’s projects are brilliant but doomed, we offer for your consideration The Amazing Screw-On Head. Based on Mike “Hellboy” Mignola’s comic, Screw-On Head is a steampunk adventure about a robot agent for President Abraham Lincoln. He battled the evil Emperor Zombie and his vampire lover Patience with the help of his butler Mr. Groin and reanimated pet Mr. Dog. The pilot featured voice work by Paul Giamatti, David Hyde Pierce, Patton Oswalt, and Molly Shannon, and was generally awesome. Sadly, it has never been turned into a full series.

Aquaman (2006): Looking to spinoff Smallville, Al Gough and Miles Millar looked into developing Aquaman. Justin Hartley (now Smallville’s Green Arrow) was to star as the titular superhero who learns of his Atlantian heritage during a trip inside the Bermuda Triangle. The producers planned out, but only filmed the pilot, which enjoyed some success on iTunes.

The Graysons (2008): After failing on Aquaman, the CW looked into the origin story of the Boy Wonder. The Graysons was envisioned as a replacement or companion for Smallville, and would follow Dick Grayson, the future Robin, through his days as part of a family acrobatics act in a traveling circus. The network decided it was nixing the series less than five weeks after it was announced, which is probably all for the best.