Surf's Up! - S1.E5

Stacey wishes she were a surfer, and during the night, sneaks over to old lady kora's house, and complains that her parents won't let hehr surf because she's too young. Stacey is immediately transformed into a teenage version, with Kendall looking the same, who growls at her for pulling her into this. They see their friends and they all realise they're in Oahu, Hawaii, where some of the biggest waves hit the sand, so Stacey learns how to surf, and is doing it like a pro. Kendall and Donnie stay out of it though, as Kendall listens to her parents and Donnie is secretly afraid of falling, when Stacey hits a bad wave and is washed right under. Finally, everybody realises how far out she went and nobody is game enough to go after her. Kendall wants to rescue her sister, and she had been watching over the surfing lessons, so she goes after Stacey and recovers her, and Stacey apologises, and she's changed back. The next day, their parents give in and take the twins to the beach,