Fountain of Youth

The Pool of Youth was a pool in the The Super Mario Bros. Super Show! episode "Two Plumbers and a Baby / Lost Dog". This pool can make any person any age they want. There is a level near the pool that can change the age the Pool of Youth will turn people into. Three old people tried to become 18 again, however King Koopa pulled the level and made the old guys turn into babies instead. Princess Toadstool then fell in the Pool of Youth and was turned in a baby version of herself.

Mario and Luigi later put the Pool of Youth back to where it was and turned the princess to her normal age and a lot of babies back to their old age. King Koopa was then thrown in the Pool of Youth and turned into a baby.