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, board books, and comic book stories starring Mickey Mouse and Pluto, but unlike Donald's nephews, they rarely show up in animation.
In pre-World War II Mickey 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 original planned name for Mickey, Mortimer Mouse, and Ferdie (sometimes misspelled "Ferdy") is short for "Ferdinand."
The twins' first film appearance was the 1934 Mickey Mouse cartoon titled Mickey's Steamroller. Aside from a cameo in 1938's Boat Builders, they didn't appear in animation again until Mickey's Christmas Carol (1983), with Morty playing the part of Tiny Tim. They also made a cameo appearance in the Mickey Mouse Works segment "Around the World in Eighty Days", which was later reused for the House of Mouse episode "Mickey and Minnie's Big Vacation". Contrary to what was written in their profile in Disney Dossiers, they do not appear in Mickey's House of Villains, though it is possible they could be among the mouse orphans seen in Gulliver Mickey, Orphans' Benefit, and Orphans' Picnic.
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. Both were anthropomorphic dogs. Ferdie never vanished from comic book stories, however.
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 & Ferdie are also occasionally pitted against their antagonists Melody, Minnie Mouse's niece and Pete's twin hellion nephews, Pierino & Pieretto. Also, Morty is a playable character on the PlayStation 2 game Disney Golf. Both Morty and Ferdie were seen in the portal to Mickeyjunk Mountain in the 2010 game Epic Mickey.