This is the glitches found in Donkey Kong Country 2: Diddy's Kong Quest
Castle Crush Glitch
WARNING:The following glitch can erase files or corrupt game cartridges if performed.
The Castle Crush glitch has become infamous among fans as the series' most fatal glitch. For players brave enough to try it, enter Castle Crush with Diddy Kong as the lead character (Dixie is optional but cannot be the lead character). Pick up the first DK Barrel and hold it against a wall. Drop the barrel and quickly pick it up again; if done correctly, the barrel will break but Diddy will act as if he's still holding it. Upon throwing the "invisible barrel", various things could happen. Commonly the Rambi Barrel will appear and cause Diddy to transform into various things, including a solid black sprite of Kleever or a multi-colored Klubba, to name a few. The effects are short lived though as any attempts to move will result in the game crashing.
The aftermath of the glitch varies. Though some have been lucky to escape with no ill effects, others have reported save data being erased, or the game becoming corrupted to the point of being near unplayable. Therefore, it is wise to avoid this glitch at all cost.
Note: This glitch only works in the Super Nintendo version. It was fixed for the Virtual Console.