You may also be looking for the episode called Nobody Smurf.
Nobody Smurf (Original French name Le Schtroumpf Sans Nom) is a character who only appears in the cartoon series. He's a Smurf with very low self-esteem.
In the titular cartoon episode Nobody Smurf, an evil goblin named Mystico escapes and transforms the Smurfs into goblins-based exaggerations of their names, such as Brainy Smurf becoming a nonstop-talking goblin or making Hefty Smurf's arms so strong that he had trouble moving.
Nobody unwittingly defeats the goblin by putting the Golden Goblet on his head after ensuing a chase. He tells him he is "Nobody" which enrages the goblin so much; he cannot hex this particular Smurf, and is soon imprisoned. Once trapped, the other Smurfs revert back to normal. Papa Smurf says that because Nobody saved them from the goblin, "You are a somebody", which inspires a more confident Nobody to change his name to Somebody Smurf.