Elmer

Elmer is a baby mouse that was found on Mickey Mouse's doorstep in Mickey Plays Papa.

Background
Elmer was left in a basket on Mickey's doorstep by his mother, who apparently poor and wanted him to have a better upbringing. His cries caused Mickey and Pluto to think he was a monster, but found him in the basket and decided to adopt him. Mickey and Pluto attempted to nurture and entertain him, but their attempts only made him cry until a mishap caused Mickey to resemble Jimmy Durante, causing him to burst into laughter.

Personality
He is shown to be bratty and hard to please, but he ends up laughing at what he finds very amusing, such as Mickey imitating Jimmy Durante.