Which animated mouse character was originally going to be called Mortimer?

Walt Disney began his first series of fully animated films in 1927, featuring the character Oswald the Lucky Rabbit. When his distributor appropriated the rights to the character, Disney altered Oswald’s appearance and created a new character that he named Mortimer Mouse; at the urging of his wife, Disney rechristened him Mickey Mouse.

An American actor named Mickey Rooney, (September 23, 1920 – April 6, 2014) claimed that during his time performing as the title character of the Mickey McGuire film series (1927–1934), he met Walt Disney at the Warner Bros. studio, inspiring Disney to name the character after him. Disney historian Jim Korkis argues that Rooney's story is fictional, as Disney Studios was located on Hyperion Avenue at the time of Mickey Mouse's development, with Disney conducting no business at Warner Bros.

Over the years, the name 'Mortimer Mouse' was eventually given to several different characters in the Mickey Mouse universe: Minnie Mouse's uncle, who appears in several comic stories, one of Mickey's antagonists who competes for Minnie's affections in various cartoons and comics, and one of Mickey's nephews, named Morty.