A Random Pebble

A Random Pebble is a cameo character who first appeared in A (Not So) Grand Return. He is a pebble with powas that can enable him to fly or fire lasers at others.

A (Not So) Grand Return
A Random Pebble first appeared when Mario threw him at Protobot at the last second and defeated him. The next time the pebble appeared was to throw Pera into the wilderness. In Chapter 7, he used his powas to cross the finish line before CK could, winning the race. Later A Random Pebble mocked Skip because he was powerless.

Not So EPF-B
In Rise of Deh Toliet Master, A Random Pebble makes a cameo while everyone is screaming due to Gary's experiment on The Party.