Elena of Avalor (2016)

S1E4 Island of Youth

As the castle gets ready for a surprise celebration for Esteban, Elena and Mateo whisk him away on a sailing trip to an island rumored to hold the Fountain of Youth. However, when Esteban indulges in the magical water, he unexpectedly begins to revert to a younger age. It's up to Elena and Mateo to rescue him from the chaotic consequences of his youthful transformation.