Sockop

Sockops are sock-like plant enemies in Mario & Luigi: Bowser's Inside Story. If Mario or Luigi try to jump on them, they will be sucked into the hole on the top of the Sockop's head. This may also cause poison. They attack by tackling the brothers.

Late in the game, Mario is captured by the Sockops and Luigi has to rescue him, getting stuck inside a Sockop in the process. While he is stuck inside a Sockop, Luigi can communicate with them, and doesn't have to fight them.

Trivia

 * Sockop is similar to the Kuribo's Shoe, a power-up found in Super Mario Bros. 3. At a certain point, it's even used to ride and hop on thorns. In addition, one Sockop's name is revealed to be Kuribo.