Rest (ねむる, Sleep) (named Sleep on the original Super Smash Bros. website) is Jigglypuff's down special move in all games of the Smash series. Jigglypuff turns toward the screen and falls asleep for about 3 seconds. Before Jigglypuff falls asleep, any opponent in contact with it is instantly hit, with a ping sound being heard. This attack is nearly infamously known for having high knockback, zero startup lag (as it hits on frame 1), very small range, and a long vulnerability period. However, Jigglypuff gains invincibility for about 25 frames, approximately the time it takes to close its eyes.
In Super Smash Bros. and Super Smash Bros. Melee, Rest is a powerful move that deals high damage and knockback. In Melee, it can be combo'd into using some of Jigglypuff's moves, such as up throw or up aerial, and it can KO reliably at as low as 25%. It can even one-hit KO the Fighting Wire Frames in Cruel Melee. However, during the transition from Melee to Super Smash Bros. Brawl, it was heavily nerfed (with its KO power being drastically reduced so that it starts KOing reliably only at 75%). It was subsequently buffed in Super Smash Bros. 4, but not back to its Melee power.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
The Super Smash Bros. version of Rest is completely different from the Pokémon version. In Pokémon, Rest is a Psychic-type status move introduced in Generation I that does not do damage to opponents; instead, it puts the user to sleep for two turns in exchange for recovering all of their HP back to maximum and healing any status ailments. The two turns of sleep may leave the user open to their opponent's attacks or setup, unless the user has an item or Ability that can cure the sleep early.
In the Super Smash Bros. series, Rest also puts the user to sleep and leaves it vulnerable in exchange for a powerful effect, but instead of healing damage, it deals damage with very powerful knockback if used right next to a foe. In the description of one of its Melee Smash trophies, as well as in Snake's Codec Conversation about Jigglypuff, it is stated that this is because at the instant Jigglypuff falls asleep, a huge buildup of energy forms at the center of its body. This is an example of the Smash producers changing the functions of a move to suit the games; other examples of this from the Pokémon series include Withdraw and Double Team.
In every Pokémon generation, Jigglypuff can learn Rest by leveling up, being one of the few Pokémon that can do so. Also, nearly every Pokémon can learn Rest via TM44.