Salvo the Slime
From the Super Mario Wiki
Salvo the Slime, also known as Big Slime, is the boss of World 1 in the game Super Mario World 2: Yoshi's Island. Salvo is a Lemon Drop that was enlarged into a Slime by Kamek. Salvo jumps at the player, trying to push them into a lava pit below his arena, though unlike most enemies, the player is not hurt by Salvo's touch. Instead, the Yoshi is hurt by the Lemon Drops that Salvo summons. Because Salvo was a Lemon Drop prior to his transformation, Lemon Drops break off of Salvo when he is hit by an egg. The more Salvo is hit, the smaller he gets, until he disappears altogether. He also is seen in the end of Door 2 in 6-8: King Bowser's Castle. Before the door with him, there's an Egg-Plant that produces eggs.
Salvo the Slime also makes two appearances in Tap-Tap The Red Nose's fort. After the player defeats Salvo in Tap-Tap The Red Nose's fort, they will get a key. Unlike the prior boss fight, Salvo can disguise himself as a box. Another difference is that when an egg hits him Lemon Drops won't come out of him.
Salvo makes an appearance as the boss of the second floor of the Duel Tower in Mario Party Advance. This game shows that he is capable of speech. Salvo then challenges the player to a game of Volleybomb, and, once he loses, the reward is the mini-game.
He also makes a brief cameo alongside other Super Mario World 2 bosses in the opening to Yoshi's Island DS.
Names in other languages