Brainy is told by Papa Smurf to make sure the other Smurfs do not disturb him while he is mixing highly dangerous potions together in his laboratory. However, in his doing so, Brainy ends up creating an accident that causes Papa Smurf to turn invisible. As Papa Smurf looks through his books for the cure, he also sees that his little Smurfs have decided to take the day off work in the village and go spend the day playing games without his permission, so he decides to have a little fun "teaching them a lesson" while being invisible. Eventually Papa Smurf finds the antidote, but in order for it to work, they need the whisker of a cat, which means they must go to Gargamel's castle and pluck a whisker from Azrael's face. As Brainy and Smurfette help Papa Smurf accomplish this, Gargamel notices two of the Smurfs and capture them. Papa Smurf, who is still invisible even after mixing the antidote together and ingesting it, takes advantage of his condition and acts as a ghost to haunt the evil wizard and send him cowering in a corner. But as Papa Smurf gets the key from Gargamel, he starts turning visible again and is caught by the evil wizard. Smurfette causes a cage to fall on top of Gargamel, knocking him out and allowing the Smurfs to escape. Back in the village, Papa Smurf gets his little Smurfs back to doing their chores and gives Brainy an earful through his megaphone.
This episode has the following tropes:
- Agony of the Feet: Brainy accidentally runs over Papa Smurf's foot with his two-wheeled cycle.
- Gossip Evolution: Brainy saying that Papa Smurf disappeared gets turned into Papa Smurf "smurfed his beard", which gets misheard as something else, and so on.
- Invisibility: What Papa Smurf goes through being in this episode.
- Invisible Jerkass: Papa Smurf becomes this to his little Smurfs when he sees them slacking off.
- Literal Ass-Kicking: Papa Smurf gets kicked in the butt by a Smurf while he's invisible.
