Don's Fountain of Youth (1953)

"Donald's trick at the fountain of youth is cut short by an alligator."

While traveling with his nephews, Donald is disgusted that they are only interested in comics. He stops at the "fountain of youth" and tricks the kids into thinking he is a baby again. However, he gets tangled up with an aggressive mother alligator and her babies, and makes a hurried exit with the nephews.