From the Super Mario Wiki
Retrieved from "https://www.mariowiki.com/index.php?title=Heart_Boost&oldid=2306240"
A Heart Boost is an item that appears in Donkey Kong Country Returns, Donkey Kong Country Returns 3D and Donkey Kong Country: Tropical Freeze. It can be purchased from Cranky Kong's Shop for ten Banana Coins. When Donkey Kong, or alternatively in two-player mode, Diddy Kong, equips a Heart Boost before entering a level, his maximum health will increase from two hearts to three for the duration of the entire stage, even if the player should lose any lives. When Diddy Kong is on Donkey's back, the duo will have a grand total of five hearts.
Names in other languages