Knock Knock is a 1940 animated short subject, part of the Andy Panda series, produced and directed by Walter Lantz. The cartoon is noted for being the first appearance of Woody Woodpecker, and was released by Universal Pictures on November 25, 1940.

The cartoon ostensibly stars Andy Panda and his father, Papa Panda, but it is Woody who steals the show. The woodpecker constantly pesters the two pandas, apparently just for the fun of it. Andy, meanwhile, tries to sprinkle salt on Woody's tail in the belief that this will somehow capture the bird. To Woody's surprise, Andy's attempts prevail, and Woody is taken away to the funny farm—where his captors prove to be crazier than he is.