The Multi-Bear is a magical beast that dwells in the mountains near the small town of Gravity Falls, Oregon. It appears in the Gravity Falls episode "Dipper vs. Manliness".
In "Dipper vs. Manliness", Dipper Pines encounters a race of testosterone-driven minotaur-style creatures called manotaurs and persuades them to teach him how to be a man. After passing a series of rigorous tests, Dipper is told by the manotaurs to slay their "greatest enemy", the Multi-Bear.
Dipper climbs high up the mountain and finds the Multi-Bear's cave, challenging the beast. Dipper's small, agile frame allowed him to gain the upper hand over the hulking Multi-Bear and he brought him down. Before he made the killing blow, however, he granted the creature one last request. The Multi-Bear wished to die listening to his favourite song: Disco Girl by Icelandic pop-group BABBA. Dipper was surprised to find that he wasn't the only one who enjoyed listening to "girly" pop music and realised that the Multi-Bear was actually a nice guy, and so he refused to kill him.
The Multi-Bear appears to be made up of a mish-mash of different bear parts. Its body is made up of five bear bodies conjoined together: two fused bodies making up the main body, two upper bodies that each form a leg, and another whole bear attached to the creature's back. The beast has eight heads: the main head which is the primary brain of the creature and is capable of human intelligence and speech, four bestial heads surrounding the main head's neck area, a head on each "leg", and the head of the bear fused to the back.
The Multi-Bear is seen to be a fairly no-nonsense type, quickly dismissing Dipper as yet another challenger doomed to die, and warning him away in light of that fact. He is not afraid to defend himself, as despite Dipper's young age, he puts up quite a fight. Once bested, though, he shows that he is surprisingly humble and honourable, making no attempts to reverse his fate, but merely requesting that he listen to his favourite song one last time. He also seems to have a lighter side, as he gets rather animated when discussing his love for BABBA with Dipper. Underneath his fierce exterior, it would seem he is a fairly gentle soul, displaying many human qualities.