Sing

Sing is a Normal-type move recurring throughout the Pokémon series, and Jigglypuff's up special move in the Super Smash Bros. series. Unlike other up special moves, Jigglypuff does not get sent into the air, but instead sings, sending out soundwaves that cause any opponents caught in them to fall asleep like in the games of origin. In Super Smash Bros. opponents with less damage remain asleep for longer, but in Super Smash Bros. Melee onward, opponents with more damage remain asleep longer, but can wake up faster by tapping the Control Stick or Circle Pad rapidly.

In Super Smash Bros. for Nintendo 3DS / Wii U this move is given two custom variants:

The first one is Hyper Voice, another move from the Pokémon series, which is an attacking variant that has greater range and deals greater damage as it goes on. Unlike with Sing, Hyper Voice can affect airborne targets, but Jigglypuff is still vulnerable while using this move.

The second is Spinphony, where Jigglypuff creates three sound waves that can flip any opponents who get hit. However, the attack takes a very long time to execute, as its startup time and execution period are both very slow, and the sound waves deal very little damage to opponents as well. Spinphony is often considered to be the worst custom special move in the game, because of its flaws making it very impractical to even be using.

Trivia

 * In Super Smash Bros. Melee, a CPU Jigglypuff uses this move after using up all of its mid-air jumps, which causes it to get KO'd if it's trying to recover.