Mortimer Mouse is Mickey Mouse's rival and secondary arch-nemesis in animation after Pete. He is a sleazy, obnoxious rat who openly berates Mickey, constantly antagonizing him for years. Mortimer first appeared in the Mickey Mouse short Mickey's Rival and ever since he has been battling Mickey for Minnie Mouse's affections.
Mortimer is incredibly selfish, rude, and constantly tries to get Minnie and Mickey to break up. Although he claims to love Minnie, he will flirt with nearly any female he sees. Minnie is rumored to be his ex-girlfriend. He seems to be hated by almost everyone, possibly even Pete, as hinted at in Pete's Christmas Caper.
- Walt Disney was orginally going to name Mickey Mortimer, but his wife insisted that it was too pompous for the character, so instead chose the name Mickey.