Rock Kroc

Rockkrocs are rare varieties of Kremlings found only in the game Donkey Kong Country. Rockkrocs, unlike other Kremlings, are brown with rocky skin and red eyes. Rockkrocs are invulnerable to any form of attack, due to their tough skin; in the Game Boy Advance remake of Donkey Kong Country, they can only be defeated while curled up by Donkey Kong's handslap move, releasing a banana or other items, such as an Extra Life Balloon. Additionally, Rockkrocs are extremely fast, allowing them to quickly dispatch anyone that invades their territory.

Donkey Kong Country
In the original Donkey Kong Country, Rockkrocs appear in only one level, "Stop & Go Station." Due to their invulnerability and high speed, Donkey and Diddy Kong must activate Stop and Go Barrels located throughout the level to prevent the Rockkrocs from moving. 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, after a few seconds, the barrels revert back to the "GO" setting, and the Rockkrocs become active again. The Kongs can also roll through Rockkrocs without taking any damage, though this is considerably riskier.

Donkey Kong Country novel
An individual Rockkroc (parsed as "Rock Krock") appears as one of King K. Rool's lieutenants at the end of the novel. Shortly after the Kongs board the Gangplank Galleon, Diddy stomps Rock Krock's head, causing him to collapse.

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.