When Mickey meets Minnie, he tips his ears in lieu of a hat.
Mickey Mouse Ears were created after Mouseketeer Roy Williams was inspired by this Karnival Kid (1929) scene. Williams created the felt caps with help from Mickey Mouse Club costumer Chuck Keehne, Hal Adelquist (general coordinator) and Bill Walsh (producer). The iconic Mickey Ears were worn by each of the Mouseketeers and popularized on the television show.
Image © Walt Disney Studios