Gulp

Gulp is one of the default moves available to Yoshi during the events of Paper Mario: The Thousand-Year Door. For the cost of 4 FP, Yoshi will swallow an enemy, and spit it at the closest grounded enemy (if there is one), damaging both. To execute the Action Command, the player must press and hold down the Button as until the gauge is full. Otherwise the move will have no effect. Yoshi can target any frontmost grounded enemy with this move, but fiery enemies will cancel out the attack, and some bosses may be to large for Yoshi to swallow, resulting in no effect. This attack pierces defense, but the damage dealt to the second enemy (the one that is spat at), is unaffected by attack buffs. Gulp also features one opportunity to perform a stylish move by pressing after Yoshi spits out the enemy.

The move has a special property that lets it bypass the special defense of the Iron Clefts. As this is the only move with this property, Yoshi is required to defeat them. Despite dialogue suggesting that the key to damaging the Iron Clefts is to find a way to make them damage each other, Super Hammer and Ultra Hammer fail to damage them. Meanwhile using gulp on a single Iron Cleft (without hitting the second) will still damage the enemy.

Unused Behaviors
Internal code shows that Gulp was intended to work differently, including different outcomes for certain enemies. For example the default outcome was supposed to be Yoshi swallowing an enemy outright, defeating them instantly without spitting them at a different enemy. This way of defeating enemies also bypassed any internal checks, such as preventing enemies from using Life Shrooms, and Bosses from doing scripted events. This particular behavior can still be seen in the released game, exclusive to single-segment Pokeys or Poison Pokeys, with a 50% of happening. Other unused behaviors include a special animation for eating exploding enemies, and spitting out a giant fireball that damages all enemies in its path (presumably for use after eating a fire-type enemy).