Stories that prove there's a fine line between zombie and vampire

True Blood returns tonight, and last season's finale dropped several clues that this season might introduce zombies alongside our usual cast of vampires, werepanthers, fairies, and shapeshifters. But are zombies and vampires really all that different?

Zombies and vampires are both, after all, the walking dead. They both need human tissue to survive. Sure, vampires tend to smell better (although True Blood's very own Pam has been defying the usual expectations of vampire hygiene) and seem more likely to leave their victims alive, but in some stories, it's hard to tell the brain-eaters from the bloodsuckers:

Daybreakers: What happens when a society made up almost entirely of vampires reaches peak blood? In Daybreakers, blood-starved vampires transform into subsiders, brutish, bat-like creatures whose hunger makes vampires look perfectly anorexic. What's interesting about the twin vampire and zombie apocalypses is that the vampire apocalypse is brought on by a plague, while the looming subsider apocalypse is being brought on by famine.

Stories that prove there's a fine line between zombie and vampire

Blade: Ninety-nine times out of 100, getting bitten by a vampire is the path to immortal life and good looks. Every now and then, however, the transformation process goes awry, turning the victim of a vampire bite into a rotting (and not terribly sane) member of the undead. In the first Blade movie, that's what happens to Karen Jenson's ex-boyfriend Curtis Webb after he's bitten by the vampire Quinn. Remember kids, keeping your skin on is the best revenge. Blade II had the Daybreakers-style Reaper virus, which turned vampires into ultra-hungry supervamps and turn their victims - even the dead ones - into Reapers.

Peeps by Scott Westerfeld: An ancient parasite starts making its way through New York, forever altering the biology of the people it infects. The luckier parasite-positives (or "peeps") develop super-strength, an irresistible craving for red meat, nigh-immortality, and extreme horniness. They're essentially vampires, save that they pass their condition through genital rather than dental contact. The majority of folks infected with the parasite, however, turn into raving cannibals who can't help but devour them in their path. These more zombified peeps do retain a sense of language — and even a dark humor — such as one peep who wrote in her victim's blood, "So pretty I had to eat him."

Last Blood: In Bobby Crosby and Owen Gieni's webcomic, the zombie apocalypse forces the last vampires on Earth to join up with the last enclaves of humans, protecting the humans so they can feed on their blood. The humans more or less take the existence of vampires in stride (after all, once you've dealt with the zombie apocalypse, vampires come off as pretty friendly), but then they learn the horrifying truth about zombies: they're created by vampires who have been starved of blood.

The Dead Undead: Vampires are also the progenitors of the zombie race in this critically panned movie. When blood-abstaining vampires are infected with a blood-borne disease, they're transformed into zombie-vampires, mindless, rotting sacks of pure feral hunger. Naturally, it's then up to the vamps to wipe out the zombies before the infection spreads to the human population. The late Forrest Ackerman actually has a brief posthumous cameo as a wheelchair-bound zombie who is quickly set on fire.

Stories that prove there's a fine line between zombie and vampire

Hellsing: In the manga and subsequent anime series, when vampires drain their victims, those victims usually turn into zombie-like ghouls, not vampires. Only virgins who are of the opposite sex of the siring vampire turn into powerful, intelligent bloodsuckers. If you're of the same sex, or sexually experienced, then a vampire bite turns you into just another member of the vamp's ghoulish horde.

Resident Evil: While in many stories vampires can create zombie-like creatures, in the Resident Evil film series, the zombie virus can create vampire-like creatures as well. Most people infected with the Tyrant virus turn into mindless, rotting, flesh-seeking corpses, but there are a few exceptions. When Alice is regenerated with a strain of the T-virus, she develops super strength and accelerated healing. When Albert Wesker is revived with the help of the T-virus, he gets similar, if more grotesquely extreme powers. He retains his intellect, develops incredible healing powers, and gets these neat tentacled mandibles, but needs to constantly consume human DNA to keep the virus under control, making him a bit more vampire than zombie.

Impaler: The vampires who invade New York in William Harms and Matt Timson's Top Cow comics are more demonic than traditionally vampire or zombie. But when they start chowing down on the denizens of the Big Apple, the effect is very similar to the zombie apocalypse. But as the series' title suggests, their deaths still require a stake to the heart, not a gun to the head.

Damn Nation: There's a similar vampire/zombie apocalypse in the Dark Horse comic Damn Nation by Andrew Cosby and J. Alexander. While the vampires spreading through the lower 48 United States are blood hungry and deathly allergic to sunlight, they're the result of a virus and look more dead meat than Dracula. The soldiers looking for a cure for vampirism even refer to the ghoulish groups as "hordes."

Stake Land: And from movie land comes yet another bloodsucker apocalypse, one where vampires have eradicated most of the living and transformed America into a wasteland. Newly undead vamps look pretty classic — mostly human, save for those giant fangs — but after a while, the blood-drinking dead start to get a bit rancid.

Stories that prove there's a fine line between zombie and vampire

The Zombie Hunters: Jenny Romanchuk's webcomic is set on a survivalist colony during the zombie apocalypse, where most residents live a rather peaceful and zombie-free existence. Since they don't have to worry about constant zombie attacks, the island's medical teams have time to work on their zombie cure, which they test out on a captive zombie. The experiment's result, Charlie, regains his intellect and stops rotting, but he still has consume human tissue from time to time, usually (and unhappily) sucking down a bag of blood. So Charlie goes from human to zombie to something in between: effectively, a vampire.

I Am Legend by Richard Matheson: Director George Romero has cited Matheson's apocalyptic plague novel as an inspiration for his zombie-initiating classic Night of the Living Dead. The infected "vampires" Robert Neville battles have a few things in common with vampire mythology: they don't walk around in daylight, are repelled by garlic and religious symbols, and transmit their infection through blood. But their mindless devotion to seeking out the living provided great fodder for what would eventually become the zombie genre, drawing a straight (if narrow) line between vampires and zombies.

And, of course, there's Pam, the True Blood vampire who spent half of last season rotting like a zombie. What other zombies and vampires straddle the line between walking and bloodsucking undead?