In Real Life
, most animals' innards are basically tubes: a mouth at one end, an anus at the other, so food can be processed step by step as it passes from entry to exit. In fiction, it's not uncommon for creatures to omit the latter portion, and double up on the former: they'll have a spare head on the tip of a tail, or symmetrical bodies in which the forequarters of two animals -- sometimes of the same species, sometimes different ones -- are joined at the waist.
If the two heads have separate brains, or come from different species, expect plenty of arguments between the two
. Fridge Logic
issues of how some of these creatures relieve themselves are primly ignored
- In the comic strips of Cricket, a children's magazine, the earthworm is treated as two characters: its front end, George, and its back end, Tail. The pair of them have different personalities.
- In 9, the Seamstress is a mechanical horror with a doll's head at one end and the salvaged upper body of a soul-drained stitchpunk at the other.
- One of these creatures was spotted in the cavern from the film Evolution, during its bug-dominated period.
- One strange sea serpent-like creature in Spy Kids 2 initially appears to have two side-by-side heads, but later is revealed to be designed in this manner.
- Two hunters ask their guide to settle a dispute between them as to which animal is the angriest: the lion or the crocodile. The guide answers that it's neither, the angriest animal is the crocolion, a beast that's the front half of a lion and the front half of a crocodile joined in the middle. The hunters protest that this animal can't exist, being unable to poop. The guide answers "Why do you think it's the angriest animal of all?"
- An earthworm pops its head out of the ground and sees another earthworm do the same. The first earthworm says "Wow! You're the most beautiful worm I've ever seen! Will you marry me?" And the other earthworm says "I can't, silly! I'm your other end!"
- In the Doctor Dolittle novels, the Pushmi-Pullyu is an antelope with two front halves, attached at the waist.
- In the film adaptations, it's a two-front-ended llama: a creature actually mentioned in Peruvian folklore.
- In After Man: A Zoology of the Future, the terratail is a subversion: it has markings on its tail that make it resemble a snake, allowing this small rodent to perform a Backup Bluff when threatened by predatory birds.
- One of the many weird critters from Wayne Barlowe's Expedition is a similar subversion, sporting an entire simulated head on its rear end to confuse predators as to which way it's facing.
- In Mythology, the amphisbaena (literally "both-way goer") was a snake or snake/bird Biological Mash Up with a deadly-venomous head at each end of its body.
- Some versions of Cerberus and the Chimera give these creatures living, biting snakes for tails.
- Another mythological example is the Egyptian Akeru: the front halves of two lions, joined in the middle. Often depicted with a solar disc on each head, it was symbolic of sunrise and sunset.
- 1st/2nd Edition Dungeons & Dragons had a giant Amphisbaena snake with a head at each end.
- The serpentir is a skeletal undead creature consisting of two human upper bodies attached to either end of a snake's spine.
- Girafarig from the Pokémon games is a giraffe with an extra spherical head on its tail.
- A whole series of inversions (two bodies joined at a shared cranium) appear in Earthworm Jim, most notably Professor Monkey-for-a-Head.
- In a Body Horror style, Thrill Kill has Judas, conjoined twins connected at the torso in such a way that there are heads at each end.
- Twingersnap from Viva Pińata is a snake with a head on each end. It can give rise to Fourheads, which has three heads on one end and one on the other.
- Diplocephalus in Castlevania: Symphony of the Night is a crocodile-like beast with the upper body of a fireball-slinging human woman attached to its tail.
- In the Facebook game Hatchlings, the hippogriff egg hatches out a creature with a beaked, horse-like head at each end.
- Google "two-headed", and you'll find plenty of photoshopped examples. (Also plenty of Body Horror: be warned!)
- The whole premise of the animated series CatDog.
- In Porky In Wackyland, there's a half-dog, half-cat creature (an ancestor of CatDog, maybe) that continually fights each other.
- On one of The Simpsons "Treehouse of Terror" episodes, Bart puts Snowball II and Santa's Little Helper through a teleporter and they come out as two different pets: one with both heads, ("Twice the pet with none of the poop!") and one with both butts. ("Eww! You can be Lisa's.")
- During the "Pink Elephants on Parade" number in Dumbo, two of the elephants cross through each other and briefly become this.
- Futurama gives us the pukeme-poopyou, a two-headed goat that continually ejects vomit/diarrhea from either end, filling a pool that the loser of a contest will have to jump into.
- An episode of Dragon Tales gives us Meow, the Copy Cat, a literal copycat with two cat heads (one at each end of its body) who had the power to make someone act like another person just by licking their face. The only way to reverse the effects of Meow's spell was to have her lick the affected person a second time.
- Some caterpillars subvert this trope, sporting false eye-spots and other features that make their rear ends look like heads as a decoy for predators.
- Likewise, some tropical fish have eyespots on their tails for this reason.
- Ischiopagus Conjoined Twins can resemble this trope, while vertical craniopagus conjoined twins are inversions.
- A Native American petroglyph in Utah depicts a bighorn sheep with heads on both ends. Another petroglyph from Tibet portrays a yak with heads on front and back.