FatKat is a character who was first seen in a HTF Break. He has only appeared once, which was in Take Your Seat. He was based off the mascot of FatKat, the animation company responsible for the TV series' animation.
A fat, blue cat who seems friendly and generally passive like most characters. His tail is different from the other tree friends; his isn't bushy, instead it is thin. A notable feature about him is the bandage on his tail. He wears a large shirt that has orange patterns traveling along the collar, the bottom of the shirt, and the sleeves. Another unusual feature about FatKat is his teeth, which unlike the other characters who have buckteeth, he has single showing, like Cro-Marmot. His ears also seem to be different from the other tree friends, ending in points instead of curves.
Not much is known about his personality, in his only appearance he is depicted as happy, and freaked out when Flaky died from the broken sea, indicating a Giggles-esque mood.
Aside from this, it is unknown if he will make any other appearances in the future, but this is unlikely due to the company not even existing anymore.