Morty and Ferdie Fieldmouse are Mickey Mouse's twin nephews, who first appeared in Floyd Gottfredson's Mickey Mouse Sunday comic strip continuity titled Mickey's Nephews (published in 1932). Since then, they have appeared in lots of comic strips, storybooks, and comic book stories starring Mickey Mouse and Pluto, but unlike Donald Duck's nephews and Goofy’s son, they have very rarely ever appeared in animation.
The twins first appeared in Mickey's Nephews on September 18, 1932, introduced by Gottfredson as the children of the nanny-like Mrs. Fieldmouse (the character who was later retconned as Felicity Fieldmouse, Mickey’s older sister). The debut consisted of the boys getting into all sorts of trouble around Mickey's home until Mickey resorted to restraining and reading stories to the boys to keep them calm.
In pre-World War II children's storybooks produced by the Disney studio, the nephews were usually called Morty and Monty rather than Morty and Ferdie. Very early books contain three or more nephews with various names, including Maisie and Marmaduke. Morty's name, short for Mortimer, is possibly in reference to the originally planned name for Mickey (Mortimer); and Ferdie (sometimes misspelled "Ferdy") is short for "Ferdinand."
Ferdie disappeared from the Mickey Mouse comic strip in 1943 because Gottfredson thought the nephews were too much alike. He had plans to bring Ferdie back later as a bespectacled, intellectual, bookworm mouse with an Eton hat and coat, with the explanation that he had been away at school. However, Gottfredson never got around to bringing Ferdie back and Morty remained in the strip alone. Morty was occasionally depicted with his best friend named Alvin, and a sweetheart named Millie.
In recent years, some of Morty and Ferdie's comic book appearances have portrayed them as football players on the team Riverside Rovers. Their mother is depicted as a supportive "Soccer Mom." Morty and Ferdie are also occasionally pitted against their antagonists, Pete's twin hellion nephews, Pierino and Pieretto.
Some merchandise for Mickey's Christmas Carol oddly refers to Morty's character only as Tiny Tim without mentioning Morty's name, even if the other characters have both their character and "actor" names listed.