Who was Mortimer Mouse and whatever happened to him?

Mortimer was Walt Disney’s original name for a cartoon mouse in the
historic 1928 cartoon “Plane Crazy.” When Walt came home and told
his wife about the little mouse, she didn’t like the name “Mortimer”
and suggested that “Mickey” was more pleasant-sounding. Walt
thought about it for a while and then grudgingly gave in, and that’s
how Mickey, and not Mortimer, went on to become the foundation of
an entertainment empire.