Crystal Star (DK: Jungle Climber)
From the Super Mario Wiki
Crystal Stars are a one-time use invincibility item in DK: Jungle Climber. Donkey Kong and Diddy Kong can earn a Crystal Star after collecting 100 jewels, causing a Crystal Star to appear on the bottom screen. If the player taps a Crystal Star on the bottom-right screen, it temporarily makes the Kongs invincible. The Kongs can carry up to six Crystal Stars at a time.