Everybody sounded the same when they hit the ground. It was weird. Even Maggie sounded like a fairly decent-sized person when she hit the ground, and she had neither the girth nor the height to produce a sound like that after the fall. I think this is probably what's annoying me the most about this clip. (Apart from the mimics of the voices getting progressively worse as the joke carried on.)
And, yes, I do recognize that it's insanely weird to focus on the physics of a falling body instead of the main topic at hand. Especially since we're dealing with a cartoon here, and the sound effects used in a brief joke aren't normally called into question in these sorts of things.