Fountain of youth

A fountain of youth is a legendary spring of water that is supposed to bring rejuvenation to whoever drinks of it.

Mainstream Smurfs Media
In mainstream Smurfs media, the Smurfs have encountered a fountain of youth in two separate locations, one which de-aged Papa Smurf into a young Smurfling, and another which partially de-aged Grandpa Smurf into a young Smurfling, though he still retains his beard.