Sworm

Sworms are black worms found outside Beanbean Castle Town in the game Mario & Luigi: Superstar Saga. They have two methods of attack – burrowing into the ground and popping back out beneath Mario or Luigi, or burrowing underground, popping up in front of one of the Bros. and biting him. The former method can be countered by jumps, and the latter by Hammers.

Trivia

 * The name is likely a pun on "Worm", due to the fact that they are underground, poppoing their heads up from the ground.