In Episode 8 of Ricco Harbor, a secret 1-Up Mushroom can be obtained through an obscure set of interactions with three duck intertube-riding Piantas. Since they are not interactable while in the water, it is only possible to interact with them by waiting long enough at certain low areas by the water. Once all three Piantas have been talked to, the last one you speak to will reward you with a 1-Up at the starting location of the episode.