Guernsey's project director, Melissa Breyer, writes in the catalog that Disney thought the train whistle sounded like "maowww-a-mouse" and dreamed up a new character called Mortimer Mouse.

Outside of Disneydom, "The Adventures of Mortimer Mouse" is also a children's book by Charlene McCoy.

Mortimer Mouse is a cartoon character created by Walt Disney and used in Walt Disney films and stories.

In the 1936 cartoon short Mickey's Rival, Mortimer Mouse was introduced as Mickey's competition for Minnie's affections.

Mortimer Mouse also appeared in a non-speaking cameo in the Mickey Mouse Clubhouse episode Minnie's Birthday, sitting beneath a tree, playing a guitar.

Walt showed a drawing of the cartoon mouse to his wife and told her that he was going to name it "Mortimer Mouse."

The Imperials (Mortimer Mouse)

Disney's House of Mouse (Mortimer Mouse, Lumiere, White Rabbit, Card)

On a train ride from New York City to Los Angeles, after a serious business setback, Mr. Disney came up with a new character: Mortimer Mouse.

"Mortimer Mouse" had been Disney's original name for the character before his wife, Lillian, convinced him to change it, and ultimately Mickey Mouse came to be.