This is one of the best (hmm, I think I've said that a few times already . . . ): from Busy Buddies. Moe sends Curly through a fence to milk a supposed "cow," actually a bull, on the other side. Twice we hear a moo, a crunch, and then we see a dummy fly through the air, land head-first, and turn into Curly. Both spills are in the first minute of the video below. (There is a third attempt, but it ends with Curly hanging from overhead wires.)
[youtube=425,350]mwdnYHL4A7U[/youtube]
The second landing of the dummy is a rare instance in which the action looks continuous, as if it were actually Curly being thrown through the air, and I think is all the funnier for it.