You can see previously posted Disney/Pixar/Marvel mashups here. And check back, because I'm updating this post with more images as I find them.
Steamboat Willie/Spider-Man mashup by Andry Rajoelina Andry Rajoelina.
Mickey and Wolvie by Erin Hunting.
X-Men meets High School Musical. Via.
Mickey tortures Spidey by Jason Quinones.
The Fantastic Four meets Michael "Mike" Wazowski by Michael Pumo. See also: Wolverine meets Mickey.
Donald Duck as the Hulk by Lou Womble.
Super Skrull Mickey by Christian.
Little Mermaid and Spidey by Niels Jorgensen.
Huey, Duey, and Luey by Desty.
The Ultimate Alliance by Carlos Lerma.
Spider-Girl/Little Mermaid by Jeremy Bernstein.
The Invincible Iron Mouse by Tim Wollweber.
Buzz/Iron Man by Dave Mott.
Jack Skellington as the Ghost Rider, one of several crossovers including 101 Abominations posted here.
Iron Mouse by Rob Kramer.
Donald as Cyclops and see also Goofy as Spidey.
Wolverine as Mouseketeer by Charles Allen Harris.
Goofy as Thor by Mark Brooks.
Captain Hook as Dr. Doom by Jason Chalker.
Nemo as the Sub-Mariner and Donald as Captain America by Alberto Silva.
Spider-Mouse from Amazing Spider-Man Annual #5. Via.
Mickey as Deadpool by Samir Barrett.
Eeyore as Mary Jane Watson via these sites.
MODUCK by Ryan Dunlavey, who also draws a cute Hulk.
Mickey vs. the Punisher by alexfugazi.
Professor Xketeer by Ralph White.
Punisher/Mickey by Aracnos.
Disney Avengers by Daniel HDR.
Spider-Mickey by Robert Cook.
Mickey as Captain America by Jason Ho.
Spider-Goofy by Pasquale D'Silva.
Spider-Mickey by Stewart Kenneth Moore. See also: Donald as 70's Hulk.
Mickey vs. the Marvel Universe.
Goofy as Galactus by Adam Koford.
Venom/Mickey by Serge Kliavaing, who has posted several more Disney/Marvel mashups.
Jack Kirby-Mickey by Craig Yoe.
Beauty and the Thing - - one of several mashups A. David Lewis posted here.
Donald/Wolverine by SaiyaGina.
Donald/Wolverine #2 by Themrock.
Beast joins the cast of Monsters Inc.
Goofy/Thor by Joel Ojeda Lopez.
MODUCK by Chris Samnee.
Spider-Mouse by Mike Mayhew.
Donald Duck as Daredevil - - one of many mashups posted in this forum.
Disney Avengers - - one of several mashups by Matt Occhuizzo posted here. Via these sites.
And finally, sore loser Darkseid. Via.
*Previously: Disney/Star Wars mashups.
*Buy toys from Disneyland at eBay.