Alien worlds are weird by definition: That's why they're called "alien worlds" and not just "totally normal worlds, nothing to see here, please move along, what tentacle?" But some alien worlds stand above the others in the weirdness department - here are five of the weirdest from movies and TV, so you know we're serious.

Asgard, "Thor"

The recent blockbuster from Marvel Studios had its share of problems: Weird sitcommy tone, more dutch tilts than "The Third Man," and too few scenes of Thor's hammer smashing stuff. But one thing they got right is the alien world that Thor calls home: Asgard, where science and magic are one and the same. Asgard truly looks like not just an alien planet but a completely different dimension than the one we know, as it should be.

The Moon, "A Trip to the Moon"

Georges Méliès' early motion picture fantasy isn't a technologically accurate look at the moon, but it is one of the first alien worlds ever depicted in movies - and also one of the weirdest. The moon here is a magical place with strange creatures that disappear if struck, and the entire surface of the moon is made up of a giant face in one of the most famous images in movie history.

Backwards Earth, "Red Dwarf"

The crew of the space station Red Dwarf, such as it is, explored their fare share of bizarre alien worlds during the run of the cult BBC scifi sitcom. But one of the strangest is all the more strange because of its close resemblance to Earth: It's a version of Earth in which everything happens backwards. Patrons in bars spit beer into glasses, newspapers contain articles about tomorrow's news, etc. It's all very driew (backwards for "weird").

The Ghost Planet, "Space Ghost Coast to Coast"

"You don't have to be crazy to work here -- but it helps!" That's Space Ghost on The Ghost Planet, the outer space meatball that used to be Tad Ghostal's superhero HQ but which has now been converted to the home of Space Ghost's talk show. The former superhero, along with two enslaved villains, Moltar and Zorak, broadcasts what has to be the weirdest talk show in the universe, all from that tiny, weird planet. Weird.

Pandora, "Avatar"

James Cameron used unprecedented special effects technology to create the planet of Pandora for his scifi fantasy epic "Avatar," and it shows. Never before had audiences seen such a fully realized and fleshed out alien world, full of strange creatures and plant life, not to mention the Na'avi who call the planet home. There are reports out there of audience members who became so enraptured by Pandora that they became suicidal because of the fact that they can never visit there. Not only is that weird, it's pretty depressing, too.