Xbox 360 / PS3 / PC: BiPolar Bear can be obtained at the end of Snow World. To obtain him, the horn is needed. Blow the horn in front of the cave leading to Ice Castle, next to the horn sign, and BiPolar Bear will emerge, allowing the player to obtain him.
BiPolar Bear will maul any player, character, or enemy of any sort with less than 11 HP. The fact that he mauls even his owner seems like a bad thing at first, but over time players develop skill and work around it, because most of the time the chances of your health bar being at or below 11 HP are astronomical; in simpler terms, BiPolar Bear is only bad for you if you've an embarrassing lack of skill.
A nice bonus to this is that he'll prevent overkill because you'll know exactly when an enemy is dead. Many experienced players tend to overkill with their juggles because they'd rather play it safe than sorry, and BiPolar Bear trims that process down to speed to make playing efficient all around, and he even is as efficient for farming as he is normal gameplay because of this.
BiPolar Bear will maul any boss with less than 11 PERCENT of their HP left; notice that's a percentage, not total. BiPolar Bear is the single best pet to bring to any boss fight because of this. You get XP every time he hits the boss, so even though you're not attacking the boss you still reap the benefits. BiPolar Bear does 32-96 damage per hit; hitting 3-4 times a second.
"Weapon Effect Usage"
Like Hawkster, BiPolar Bear can freeze, shock, burn, poison, and critical hit.
BiPolar Bear's name is a reference to the manic depression known as "Bipolar Disorder" which causes extreme mood swings, often shown as open hostilities in popular culture.
BiPolar Bear attacks Pipistrello's poop (confirmed for the Xbox 360 and Steam editions).
As BiPolar Bear attacks any injured character, keep in note that it will also attack yourself if you're low on health while competing for a princess or while fighting in arenas in co-op modes.
BiPolar Bear is an SS Rank pet (SS).
BiPolar Bear combined with the Ribeye and Saracen/Bear, or Orange Knight are considered some of the deadliest and most efficient character/pet/weapon combos in PvP although Bitey Bat may be better.
BiPolar Bear can critical hit for up to a whopping 384 damage!
There Is a Bipolar Polar Bear charm in the official behemoth website for $5.00
On the Xbox 360, players can dress up their Avatar with the BiPolar Bear's head by purchasing it in the Avatar Store, in which it's simply called "Bear".
BiPolar Bear will automatically maul the Painter's paintings even at full health.