He first appears in "Headhunters," in the biker bar Skull Fracture drinking, where Mabel somehow strikes up a conversation with him. Mabel quickly wins him over with a paper fortune teller, and tells him his wife will be pretty, but he worries if she will love him.
He later appears in "Summerween," where Dipper and Mabel's cute costume and dance brings him to tears, and gives the two generous helpings of candy.
The Bats Biker may look gruff and mean, but he appears to have a soft spot for cute things.
Bats Biker has a grizzled face with a bushy black beard, sideburns, and eyebrows. He appears to be missing a few teeth, has pierced ears and a scar on the side of his face. He wears a red bandana and is possibly bald. He also has a tattoo on his right arm of a dagger with a banner over it that reads "BATS." He wears a black shirt that is ripped on the side arms. The tattoo read backwards says stab, this makes sense because behind the wording is a knife.