Biff is a big strong mouse and Squeak's best friend from mouse school.
Biff at first was skinny and the skinniest in the mouse school class. He then decided to become strong and work out. He then forced the mice to work out and made them lift cheese barbells, much to the mice's chagrin. He goes hard on the them when they do so. He also is Emily's boyfriend, since she thought he was cute. He even forced Garfield (character) to work out, much to his dismay. When he feels sad, he stops being strong and eats junkfood like Garfield, as shown in 'Fitness Crazed'