Puff Up

Puff Up (, Grand Growth) is Jigglypuff's Final Smash.

Overview
When used, Jigglypuff slowly inflates itself to a very large size, enough to almost entirely cover a small custom stage. While growing, enemies and items will be pushed away. Once Jigglypuff reaches its full size, it shouts "JIGGLY!!!" and shrinks.

In Super Smash Bros. Brawl, it causes a massive push that will most likely KO any enemies too close to its body, especially if they have used up their jumps trying to avoid it. While Jigglypuff is deflating, it will cause 17% damage and powerful knockback upon contact, similar in power to the push effect. This is in effect until Jigglypuff is back to its original size, making contact dangerous until the Final Smash ends.

Puff Up received some changes in Super Smash Bros. 4. Jigglypuff now grows to a larger size and the push hitbox now scales with damage instead of being set knockback, making it weaker at lower percents. The damaging hitbox was also changed to only be at the beginning of the deflation, only hitting once instead of allowing multiple like in Brawl.

It was changed again in Super Smash Bros. Ultimate. Just like other Final Smashes in Ultimate, this one is faster, both in inflating and deflating. Once fully inflated, Jigglypuff will quickly and briefly expand further and "pop" before rapidly deflating. It now deals 10% when Jigglypuff shouts and then an additional 25% with the "pop" instead of a 17% from the prior games.

While the move covers a very large range, it loses potency quickly on larger stages, and cannot affect anything below Jigglypuff (though this can be remedied by having Jigglypuff start the attack from below the stage, which will let it expand up and through the stage). Also, it can affect teammates even when Team Attack is off.

Glitch
There is a glitch in Super Smash Bros. Brawl where the terrain in some stages (such as Bridge of Eldin) touches Jigglypuff and knocks it out of the move, yet it remains the same size it was when it was forced out of the Final Smash. If Yoshi (or Kirby with Yoshi's ability) uses his Egg Lay on Jigglypuff after this, or Jigglypuff picks up a Super Mushroom, its size doubles, allowing Jigglypuff to become the biggest character in the game. Its size resets when it uses the Final Smash again or gets KO'd. As a pun on its enormous size, the glitch Jigglypuff is often called "Bigglypuff", "Gigapuff", or "Gigalypuff" by fans. When the glitch is performed, Jigglypuff will still have the strength it had when it was at its standard size. Jigglypuff will appear to move very slowly, having the illusion of not being able to jump very high, as well as falling slowly, all attributes equal to when it was at its regular size. As a result of these large hitboxes, should Jigglypuff roll or use its forward smash with the glitch, it will likely self-destruct, as if any hitboxes come in contact with the blast line, Jigglypuff will be KO'd.

Origin
Although Puff Up is not an attack in any game, Jigglypuff - as the "Balloon" Pokémon - is stated in the  to be capable of inflating its balloon-like body, and its   is described as being able to inflate to incredible sizes. These abilities are shown in various media such as its appearances in the anime, where a recurring individual Jigglypuff would "puff up" when angered, notably growing to an incredibly large size on one occasion during a visual gag, and one particular instance of a giant Jigglypuff that fought a giant and.

Years later,  would introduce the concept of ing, where a Pokémon can temporarily increase its size and power immensely. While Jigglypuff didn't initially have access to Dynamax due to being cut from the game, it was later re-added in DLC.

Trivia

 * Jigglypuff's size before using the Final Smash affects the size it grows to. In a Giant Brawl, it can grow to a size where only its face is visible on screen.
 * Puff Up is one of the five Final Smashes that can affect a team player. End of Day, Landmaster, Iceberg and Galaxia Darkness (in Brawl only) share this trait.
 * It is also one of the only two Final Smashes that can damage an ally directly when Team Attack is off. Galaxia Darkness shares this trait in Brawl.
 * If many characters get stuck between Jigglypuff and a wall at once, the effects get slowed down.
 * Not counting custom moves, this is Jigglypuff's only special move in the  series that does not originate strictly from the series.
 * The closest counterpart that is native to the Pokémon series is the Dynamax Phenomenon from Pokémon Sword and Shield.
 * Most of Jigglypuff's attacks cause it to look in a certain direction while performing a move and if this applies to the move Jigglypuff broke the Smash Ball with, then after using the Final Smash, it will look in that direction until it uses an attack or air dodge. This glitch can even carry over into two of its victory animations (with the third cancelling the glitch due to its eyes already being scripted to look to its right).
 * In Ultimate, if performs Kamikazee in front of Jigglypuff while it is performing Puff Up, it will temporarily make the usual shocked expression caused by Kamikazee, only to revert back once Hero is KO'd.