Salvo the Slime

Salvo the Slime is the boss of World 1 in the game Super Mario World 2: Yoshi's Island. Salvo is a Lemon Drop that was transformed into a Slime by Kamek. Salvo jumps at the player, trying to push him or her into a lava pit below his arena, though unlike most enemies, the player is not hurt by Salvo's touch. However, Lemon Drops break off of Salvo when he is hit by an egg or Watermelon Seed. The more Salvo is hit, the smaller he gets, until he disappears altogether.

Salvo the Slime (though classified only as Salvo) makes an unexpected appearance as the boss of the second floor of the Duel Tower in Mario Party Advance; interestingly, this game shows that he is capable of speech. He also makes a brief cameo alongside other Super Mario World 2 bosses in the opening to Yoshi's Island DS.

Trivia

 * Although Salvo is indeed a name (actually a surname), its use in this character's name is likely a pun on "saliva," referencing his slimy texture.