Thus was an icon born. I suppose the image of a tiny baby bird suddenly pulling out a huge and heavy anvil contributed to the humor. It occasionally gets shown at Art Movie houses as a historical curiosity. Made during the Second World War, it portrays the Japanese as heavily caricatured Bad Guys. At one point Bugs challenges a Japanese pilot to a duel in the air.
Bugs wins, and the Japanese pilot parachutes to safety.
Bugs flies by and hands him an anvil. Said pilot drops like a rock. You probably haven't seen this one, either. The kid, Butch, abuses Porky, at one point handing him an anvil that causes Porky to crash through the floor into the basement. A lot of the people I talked to thought that Tex Avery must have been the first to use the Falling Anvil gag.