Teats are funny. So (apparently) thought Walt Disney, who made them the butt of jokes in a number of his early cartoons. Steamboat Willie was among them.
Mickey Mouse attempts to have a cow hoisted onto a steamboat. The drawings below tell the gag.
This is the same cartoon where Mick plays the teats of a pig as a musical instrument. Nothing like farm humour.
Ub Iwerks rightfully gets a “By” credit as he animated almost all of the cartoon.