Piano Key Wave

A character plays the piano energetically (or even not so energetically), and the keys bounce up off the piano, move in one direction or the other in a wave, or otherwise violating the laws of piano physics. The keys may move individually, or might move as a single, flexible unit. Regardless, they always land back where they are supposed to be at the end.

Justified by the Rule of Funny.

Comedy

 * Victor Borge had a comedy bit where his piano sounds wrong... so he takes the row of keys out, flips them, and it sounds perfect.

Film - Animated

 * The Other Father does this in Coraline. Possibly justified since it's a magic piano.
 * In The Great Mouse Detective, the piano player in the run-down pub makes the keys bounce in the air in a few close-up shots.

Music

 * This occurs as a special effect in the video for the Go-Gos' song "Head Over Heels".

Video Games

 * The Beethoven level in Dragon's Lair.

Western Animation

 * The Bugs Bunny cartoon "Rhapsody Rabbit" has quite a few of these, including the piano keyboard acting like a typewriter carriage and, at one point, Bugs literally picking up the keys and letting them fall back down.
 * Also in the Tom and Jerry cartoon "The Cat Concerto". In fact, the two cartoons were so similar that Warner Brothers and MGM sued each other for plagiarism.
 * Happens several times during Mickey Mouse's piano recital in "The Opry House".
 * In the Classic Disney Short "Three Little Orphans", three kittens climb on a player piano and turn it on. The keys bounce up and down, carrying the kittens along. When the speed is turned up, the kittens are being juggled about and one is even spanked by the hammers inside.
 * Disney's Tangled features a rough-looking barbarian playing the piano with a hook for a hand, causing the keys to do all sorts of gymnastics. By the end, so many have gone flying that it's hard to believe there are any left on the piano.

Real Life

 * Yamaha's Disklavier piano, which is similar to a player piano, creates waves at parts of Animusic's "Starship Groove". What's more interesting that the piano is real, rather than animated.