Battle Arena Crown
From the Super Mario Wiki
Battle Arena Crowns, also known as Battle Crowns, are objects which resemble King K. Rool's crown, found throughout Donkey Kong 64. One Battle Arena Crown exists in each level, for a total of ten. Battle Arena Crowns are obtained by staying alive for a preset amount of time against different types of enemies. These challenges can be activated by pressing on a Battle Arena Pad, which is a large, round, mechanical pad with King K. Rool's face on it. At least one Battle Arena Crown is needed to unlock multiplayer-mode, and four are needed to open a door in Hideout Helm. All of the game's Battle Arena Crowns are needed to complete the game 101%.