Zack was Brick's friend. They met at the school's social skills group. Zack thinks he's a cat and nearly always wears mittens on his hands. He frequently meows. It is speculated that this is his coping mechanism. He has been stated to be the most popular member of the group. Zack invited Brick over to his house for a sleepover, they got on well. Until Brick offered Zack some chocolate Frankie gave Brick for Valentine's Day, but what Brick didn't know was that chocolate causes Zack to freak out. Zack's mom Beth had to call Frankie to pick Brick up. Zack appears in a few more episodes in Seasons 1-4 but doesn't play a major part in any more episodes.
However, in Season 9 he returned in Great Heckspectations, when Frankie invites him and other members of Brick's former social skills group to join Brick and Cindy at the school prom. He and the other boys have girlfriends too, and much to Frankie's surprise, has overcome his cat-obsessions.