Some make you look closer in wonder, some have extra appendages sprouting from their bodies and others are just plain strange-looking. No, it's not backstage at a village fair's vegetable judging competition we're talking about - but extra terrestrial creatures in all their weird and wonderful forms.
Inspired by ongoing research, alien life has been represented on the big screen for many years: from long-fingered, friendly little dudes like E.T. to ones you wouldn't like to meet down a dark alley, such as Predator.
And it's not just the obvious ones to watch out for, either. When they're not being all tall and blue and living on the habitable moon of Pandora or navigating small children's bicycles to get home, some otherworldly creatures in film have a habit of taking inspiration for their looks from humans.
Superman and The Coneheads make up a strain of characters that conceal their special powers under the guise of a pedestrian outfit. Although, occasionally a spanner is thrown into the works when these creatures make their debut on Earth (giveaways signs include tall, pointed craniums and caped red and blue costumes). Even Doctor Who attempted to blend into the masses with a selection of well-considered outfits - failing miserably with his extra-long scarf, of course.
Maybe it's the way that scriptwriters can be endlessly creative (and irreverent) when imagining aliens that makes them such a popular feature of modern cinema - a little bitty life form bursting from officer Kane's chest in Alien while he's innocently enjoying a bowl of noodles? Absolutely. District 9's space-faring race with their violent ways and penchant for cat food? Why not.
Whatever the reason, studies of life on other planets have fuelled the public's love of all things extra terrestrial in films.
Below we round up the good, the bad and the ugly - alien life forms, that is.
Born from John Hurt's rib cage and blasted back into space by Sigourney Weaver. What a life.
James Cameron's most successful (and lucrative) film characters to date. Sorry, Jack and Rose.
Affectionately known as Chewie, George Lucas's creation is seven feet of fur and guttural noises.
The genetically modified race from Skaro is a force to be reckoned with. Just ask the Doctor.
Everyone's favourite bug-eyed, magic-fingered alien botanist, not least his best pal Elliott.
A film from which we learn an important lesson: playing Slim Whitman songs kills aliens from Mars.
The non-humans of District 9 hail from a world with seven moons and conditions similar to Earth.
Master of the raised eyebrow long before Botox and the planet Vulcan's most famous export.
Pred's deadly insect-like jaws give a whole new meaning to the phrase 'toothy grin'.
Better-looking than a Ken doll and faster than Usain Bolt: whatever's in the water on planet Krypton, we want some.