You can't get more realistic than this tee that proclaims, Terry Bisson style, "I am made of meat!" You can find it, and proclaim your true biological function, here.

Then there's the secret history of Alien's love for Predator, which you should proclaim loud and proud on your chest. You can get the tee here, and get some alien/predator love action here [NSFW].

And just to put all of this in perspective, we have the most truthful shirt of all, which offers us a chart explaining why the humor of memes like the ones on these tees is inversely proportional to their popularity. Let the world know the true worth of memes by buying this meme-laden shirt here.

Of course no gallery of scifi-themed shirts could ever be exhaustive, but we've got a nice selection here of whimsical, artistic, and referencey. And of course, don't forget to pick up an io9 t-shirt from our Neighborhoodies collection. All proceeds from our io9 tees go to the Carl Brandon Society.

I love this Twi'lek Pinup [via StarWarsShop] - it's like the dearly-departed Bettie Page crossed with alien sizzle.

And if you're smarting over the recent remake of The Day the Earth Stood Still, you'll want to shout your loyalty to the original with this Klaatu Barada Nikto shirt [via Retropolis Transit Authority].

This shirt is called Better Recognize [via MiniCassettes] because you'd better recognize the most evil vector drawing in scifi history. (Hint: You saw it in Tron.)

Three little robots make a nice beginning for your army in a shirt called Mechanical Breakdown [via ReThink].

The shirt called The House that Romero Built [via Mediocore] is pure luxury, with those big zombies emblazoned all over your chest.

I am a huge fan of all the tees from Loyal Army, but Spaceships is the cutest space-themed tee I've ever laid eyes on.

Speaking of cute tees, Dinosaur Attack [via Divine Clothing Co] is the perfect shirt for the person who dreams of dinosaurs and giant monsters.

Wow, it's full of stars. That's right, that gorgeous, award-winning Live Long and Prosper shirt [via MadeByHumans] is basically the loveliest depiction you could imagine of the classic Vulcan greeting.

For booklovers, there's nothing better than Take Me to Your Reader [via Cameesa], an amazing shirt that shows a UFO book showering an innocent Earthling with words.

There's nothing better than a random scientific diagram of holiday-esque trees, which you'll find on the How To Shirt [via Assembly of Text].

Got Space? [via Zazzle] shows a highly-detailed view of the Hubble telescope. Basically, nothing could be more awesome than that.

Vampires Beware, by Ian Leino [via Threadless] depicts all the tools you'd find in a Victorian vampire-killing kit. Show all those Twilight fans how you really feel.

If you're feeling steampunky, tentacly, or just alternative history-ish, Two Guys & An Octopus, by Resist Today [via Shanalogic] might be just the ticket.

Captain Hammer's Duds:

Show your love for Joss Whedon's latest gift to the world, Dr. Horrible's Sing-A-Long Blog. Let the hammer in your pants jokes fly, gloves not included.

Marty McFly's Nikes:

Nike has a limited release of Hyperdunk from Back To The Future II. Be warned, wearing these amazing kicks may get you mugged by yours truly.

Scientific Explanations For Fantasy:

Don't let the scifi fantasy war get your spidey undies in a knot this year. When you're in the heaps of battle over what's magic and what's science, simply point to your chest, argument avoided.

Lightsaber iphone Application:

Carrying around an actual lightsaber is so last year thanks to the new iphone application, you can bring your camera, calendar phone and Star Wars weapon of choice to con. Extra io9 love for the first person to make the garage iphone saber youtube.

Frakkin Toaster:

Can't afford the 60 bones for the actual BSG toaster, don't fret here's an equally adorable Toaster T-shirt.

No More LaBeouf:

Take a stand against the infestation of Mr. LaBeouf in every single magazine and movie out there. Can we get a break from the stuttering "I yell No a lot" boy for at least one year please.

All The Robots That Matter:

Display your love for scifi robots in a artistic matter across your chest. I particularly like the Matrix bots.

Avatar Aliens:

If you get your hands on this T-shirt then I tip my hat to you sir because either you're incredibly crafty, worked on James Cameron's Avatar movie or Sam Worthington. But you'll be incredibly above the T-shirt curve.

And finally instead of sporting the usual Watchmen smiley face I encourage you all to vote for the Watches of the Watchmen T-shirt on threadless, it isn't in print yet but really should be.

Holy crap do I ever love that one with the scientist hugging the nuke plant. But what do I love more? Two of the tees below. First, I adore the one that says "fucking pterodactyls," a sentiment I experience practically every time Rodan steals my Prius. And the ear mouse one. Just because I've always wanted to grow an extra ear on my cat. I don't think she'd mind.

There are a lot more where these came from, including a bunch more "teach the controversy" ones (including unicorns!). And they're priced pretty reasonably, too.

Amorphia Apparel [official site]

You can see a bunch more designs at the Atomic Tarantula website. I have the "damn dirty apes" tee and have gotten a lot of compliments on it!

Atomic Tarantula [official site]

Collect them all:

Star Wars Light Saber
Firefly
Master Chief
Nuke
Phaser

Transformers T-shirt is Bad Idea at Airport [via Hide Your Arms]

• Snorg Tees prides themselves on being a pop-culture t-shirt powerhouse, but they only have three sci fi shirt designs in the midst. Thankfully, they're all sublime, ranging from the brand-new outer space sex design, to the fate of poor Pluto, and my personal favorite, the Back to the Future rebus
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• Threadless is an extremely cool "voice of the masses" t-shirt shop where people submit designs, and you vote on 'em to decide if they should be made into shirts. Since it's all submitted designs and not licensed properties, you'll get truly original stuff like The Voyage of the Space Chrysalises, Rocketbird, The League Of Cliche Evil Super-Villains, and I know we said no Star Wars, but this Dark Side of the Garden shirt with a topiary-cutting Vader is inspired.
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• Seibei has some of the stranger shirts we've seen out there, like this Strange Invaders one. However, if zombies turn out to be caused by a human-created supervirus, and not just some living dead hoohah, then you can pick up this Intramural Zombie Hunter shirt, complete with bloodstains.
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• NerdyShirts is actually much more geeky than nerdy. They have some great shirts like this Optimus Prime one that is loads better than the recent movie was, an elect Bruce Campbell in 2008 shirt (complete with chainsaw), an extremely wacky Spidermanmobile, and everyone's favorite Japanese nerdy guy, Hiro.
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• 80stees specializes in vintage-looking shirts featuring everything from Knight Rider '82, to a Better, Faster, Stronger Six Million Dollar man shirt. You can even get the Greatest American Hero's costume here, if you're looking for a new outfit. Instructions not included.
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• Palmercash has a lot of offbeat shirts, like Nixon in '78 and the like, but if you do some searching you'll find everything from this vintage-cut ladies Pixelbot t-shirt, to a day-glo Space Invaders piece of work. They're a bit pricy for t-shirts, but I brought my brother one for Christmas, and he loves the damn thing.
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• Neighborhoodies will let you design your own everything, from hoodies, to t-shirts, to boxers. They have a few ready made shirts, including this Planet Express number from Futurama, but you should feel free to let your imagination run wild. Beware, it's entirely addictive once you get started.
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• Cafe Press has an entire science fiction category on their site, but they are frequently hit or miss. They run from the sub-par to the subdued. Plus, since the fans are running the asylum, you'll see an overload of Firefly and Star Trek stuff. Not that there's anything wrong with that, we just like a little variety on our body.