Bartholomew Kuma (sometimes called simply Bart) is a bear human hybrid and a member of the SheeBookie, as well as an anti-hero. He is actually not human, but a cyborg. He is very calm, and religious, except during his severe (and quite common) cases of explosive diarrheah.
Not much is known about Bart's past. What we do know, however, is that he was seriously screwed in the head, but then some guy named Dr. Vegapunk arrived and turned him into a cyborg, where he became a puppet for the world government. Despite being a member of the SheeBookie which the marines often are on bad terms with, he is good friends with Fleet Admiral Buster Baxter.
It should also be noted that his strength is overwhelming, even for a member of the second strongest pirate organization in the world. In fact, he is so strong, he gave EVEN CHUCK NORRIS a hard time (needless to say, Chuck still defeated him, but still). Before his brutal fight with Chuck Norris, he absorbed Chuck's chestnut powers and used them in his fight against Hisa Takei, which removed her from existence. Chuck Norris, during the brutal fight with Bart, kicked the powers out of him and got them back. Bart was even able to beat Mario. Multiple times. On the brink of death.