Mortimer Mouse is Mickey Mouse's secondary arch-nemesis in animation, after Pete. He is a sleazy, obnoxious rat who openly berates Mickey, constantly trying to take Minnie away from him for years. Mortimer first appeared in the Mickey Mouse short Mickey's Rival and ever since he has been battling Mickey for Minnie's affections.
When Walt Disney was in the process of Mickey Mouse, he suggested the name of his new character to be Mortimer Mouse. However, his wife, Lillian Disney, felt the name sounded too pompous, and suggested Mickey instead. Years later, when developing a new short, the name Mortimer was put to use for a new character, an antagonistic rival of Mickey's for Minnies affections. Mortimer only appeared in the cartoon "Mickey's Rival" and was never seen in animation again until 2000, when his popularity skyrocketed and landed him roles in several Mickey Mouse related material.
Since then, in all animated appearances, Mortimer's voice has been provided by Maurice LaMarche, which is said to be an exaggerated impression of comedian Jon Lovitz.
In the comics, Mortimer was called Montmorency Rodent. In his first appearance he was called a Mr. Slicker in the cómic Mr. Slicker and the Egg Robbers, when the father of Minnie Mouse is in the danger of losing his mess of eggs, and Mr. Slicker offers him the financial help in exchange for Minnie's hand in marriage, and Mickey suspects in him. Ultimately, Slicker turns out to be the one who stole the eggs to obtain Minnie's hand.
It appears for the first time in animation in the short "Mickey's Rival", in 1936, where Minnie presents Mickey as former his boyfriend. Then, Mortimer starts doing plays to Mickey, which does that it extracts of his cabins. Then it does not return to appear up to the short "Mickey's Rival Return", in 2000, where Mortimer challenges Mickey to a party of boleybol, in that, the one who wins, he invites Minnie to a holiday that exists this night. From this shortly it appears in other six until 2001.
He is said that Minnie Mouse knows Mortimer Mouse longer than Mickey.
Mortimer Mouse was the original name for Mickey. Walt rejected this name because it wasn't that good of a name for a kids cartoon.