In "Grandpa's Fountain of Youth," a hyena is shown being chased by a cougar in the jungle. However, hyenas are native to Africa and Asia, not Central America, which is the background of this episode.
In "Grandpa's Fountain of Youth," while checking to find out how Grandpa turned to a Smurfling, Papa Smurf touched Grandpa's beard and latter found that it contains water from a fountain that turns creatures young. However, for some unknown reason, Papa Smurf did not become young even though he had direct contact with the water (through touching Grandpa's bread) as did Grandpa and the other victims.