Super Happy Tree
The Super Happy Tree is a tree that is only found on Yoshi's Island during the events of the game Yoshi's Story. It grows every type of fruit available on the island, including the magical Heart Fruit. In Yoshi's Story, Baby Bowser stole the Super Happy Tree for its power. The Yoshi's later recovered it after defeating him. It is the ultimate source of all the Yoshi's happiness on Yoshi's Island.
The Super Happy Tree is rarely, if ever, mentioned in any other game in the Yoshi series. If the Super Happy Tree did in fact disappear, it implies that all Yoshis are no longer happy.
It later appears in Super Smash Bros. and Super Smash Bros. Melee in background of a stage. It also makes a cameo in the background of Yoshi Park during Mario Superstar Baseball.