Radna is a human character that appears in the cartoon show episode "Wolf In Peewit's Clothing". He is an evil sorcerer who is looking for a way to restore his evil powers and found in a book of spells that the formula for doing so requires Smurf sweat. As he wondered how he could get his hands on Smurfs so he can get the Smurf sweat, Peewit the court entertainer visited his castle, looking for a meal to eat. Upon Peewit saying that he is a friend of the Smurfs, Radna invited him in and served him up a dinner with a special potion called wolf gravy poured on the jester's roast beef. Soon the wolf gravy had its effect by having Peewit fall under Radna's hypnotic spell, with Radna telling Peewit that he will go to the village of the Smurfs and bring his master back three Smurfs, but until then he will not remember that he has ever visited Radna.
The wolf gravy would eventually change Peewit into a werewolf by the light of the full moon, as he turned into one three times. The first time was when Peewit was in The King's bedroom trying to read him a bedtime story, causing him to run off into the forest and travel close enough to the Smurf Village to be found by Brainy and Clumsy. The second time was when Peewit went to sleep in the Smurf Village, only to capture Brainy, Smurfette, and Clumsy and take them to Radna, who rewarded the transformed entertainer by clapping him in irons and casting him in the dungeon.
As Radna had the three captured Smurfs run themselves ragged inside a cage to collect the Smurf sweat from them, Johan as well as Papa Smurf, Hefty, and Greedy sneaked their way into the castle to rescue Peewit and the other three Smurfs. This was when Peewit changed into a werewolf for the third time and broke out of the dungeon to pursue Johan and then later Radna, whose book of spells was destroyed by Peewit. Hefty broke the three captured Smurfs out of the cage, with Smurfette destroying the vial of Smurf sweat, and Johan distracted Peewit by tickling him so that Papa Smurf could feed him a garlic bud and restore him to normal. Radna saw that his plans for restoring his evil powers were ruined and thus considered becoming a good wizard instead.