In this 1969 cartoon, Mickey Mouse enlists in the Vietnam War and gets killed

"Short Subject" (AKA "Mickey Mouse in Vietnam") is a black and white cartoon from 1969 starring Mickey Mouse. Running a little over a minute long the cartoon tells the story of Mickey enlisting to serve in the Vietnam War and getting shot in the head as soon as he arrives. The film was directed by Whitney Lee Savage (the father of Adam Savage, of MythBusters ).

According to Wikipedia, "The music prominently used in the soundtrack is The Gonk by Herbert Chappell, which was popularized by George A. Romero's horror film Dawn of the Dead."

It's safe to assume the filmmakers didn't receive Disney's approval to use Mickey Mouse in their cartoon, though I would guess it falls under the use of parody.