Rock Kroc

Rockkrocs are rare varieties of Kremlings found only in the game Donkey Kong Country. Rockkrocs, unlike other Kremlings, are brown with rocks as their skin and they have red eyes. Rockkrocs are invulnerable to any form of attack, due to their tough skin, until the Game Boy Advance remake of Donkey Kong Country where they can be defeated when curled up by Donkey Kong's handslap move, making them release a banana or sometimes an extra thing such as an Extra Life Balloon. Additionally, Rockkrocs are extremely fast, allowing them to quickly dispatch anyone that invades their territory when the Stop and Go Barrel turns green. When it turns red, a Rockkroc will curl into a ball (and resemble a boulder).

Donkey Kong Country
In the original Donkey Kong Country, Rockkrocs appeared in only one level, "Stop & Go Station." Since they are invulnerable, Donkey and Diddy Kong must figure a way to pass by them. Unfortunately, since the Rockkrocs are so fast, it is impossible for the Kongs to pass them by jumping over them. If they land on a Rockkroc, one of them would be immediately attacked by one of the agile Rockkrocs. However, the Kongs could activate Stop & Go Barrels located throughout the level that would prevent the Rockkrocs from moving when turned to red. These barrels are normally on the "GO" setting with green lights surrounding the level, but when the Kongs hit the barrel, the barrel switches to "STOP" and the lights turn red. The Rockkrocs then curl into balls and stop moving, allowing the Kongs to continue throughout the level. However, this effect only lasts shortly. After a few seconds, the barrels would revert back to the "GO" setting, making the Rockkrocs become active again and run quickly in straight lines again and the Kongs must simply hit the Stop & Go Barrels again to stop them from moving again.

Trivia

 * Rockkrocs are the only type of Kremlings from Donkey Kong Country to never appear in the Donkey Kong Country animated series'' in any fashion.