The rainbow droplet (Japanese: にじのしずく, rainbow drop) is an item which appears in The Legendary Starfy. It is found in the level "End of the Rainbow" in Skydye Heights (Stage 6-2) within the opening of a giant clam. It appears to possess special healing powers.
In the story, Ruby asked Moe to get her a rainbow droplet to heal the wounds of Papes and Ronk. Moe was originally hesitant to help, telling Ronk to "back off" and believing that Snips and Ronk posed a risk to Ruby, however Moe's crush on Ruby lead Moe to reconsider and come with Starfy to locate the rainbow droplet. Feeding cotton candy to the giant clam caused it to close and reveal the rainbow droplet after opening.