Chomp Rock

Chomp Rocks, also known as Romp Chomps, are round stones that look like Chain Chomp heads. They appear primarily in the Yoshi series.

Super Mario World 2: Yoshi's Island
Chomp Rocks first appear in Super Mario World 2: Yoshi's Island and its remake as a common object. They are generally used for moving through soft rock and reaching high areas, but in some levels, they are an obstacle, such as when they need to be rolled off a thin pillar to reach a key. Some Sluggers hit these back and forth. Yoshi can push Chomp Rocks forward or jump on top of them to roll them in any direction. He can use Chomp Rocks to crush most enemies, even otherwise-invulnerable foes, such as a Tap-Tap.

Chomp Rocks come in gray and brown in this game, the difference being that the gray ones will respawn at their starting point if the player leaves the screen and comes back, while the brown ones will not.

Yoshi's Island DS
Chomp Rocks appear in Yoshi's Island DS unchanged from the previous game except for the fact that neither color respawns, except for the one in the Island Museum's Land Enemy section - which happens to be brown.

Yoshi's New Island
Chomp Rocks appear in Yoshi's New Island, unchanged from the previous game.

Yoshi's Woolly World
Chomp Rocks reappear in Yoshi's Woolly World, acting the same as in previous Yoshi games. In this game, they resemble amigurumi crochet spheres that come in many different color variations with white buttons for eyes. Frame Chomps can be turned into a Chomp Rock if Yoshi throws a yarn ball at one. The color of the Chomp Rock is determined by the color of yarn used.

Other appearances
Chomp Rocks appear in Paper Mario as background objects in Dry Dry Ruins, and resemble the living Stone Chomps, which are actually based off of entire Chain Chomps. They are also seen outside the Dry Dry Ruins, on decorative pedestals surrounding the outside. Paper Mario's Chomp Rocks have slightly gaping mouths.

Two Chomp Rocks appear in Paper Mario: The Thousand-Year Door in the Palace of Shadow's Riddle Tower area, blocking the pipes that Mario needs to unlock the tower. Actual Chain Chomps guard the pipes. In this incarnation, the rocks are hollow and have open mouths. Mario can destroy the rocks by throwing Admiral Bobbery into the gaping maws of the rocks. When Bobbery explodes, the rock is destroyed.

Brown Chomp Rocks make an appearance in Mario & Luigi: Partners in Time, where the Yoshis are needed to move them on two occasions to open up new paths in Yoob's Belly. Five Yoshis can also use a Chomp Rock to lower Sunnycide's defense after the Bros. free them from Yoob eggs.

In the Club Nintendo comic "Mario's Picross", Mario gets arrested inside of a pyramid. He comes across a treasure chamber with a chest inside. When trying to pick up the treasure chest, a Chomp Rock is released through a trap door and starts rolling towards Mario. He escapes from the rock by jumping into a lorry and moving away.