A sweltering heat wave has Brainy decide to create a batch of smurfberry juice that he would enjoy all for himself, but he finds out that the heat wave has affected the smurfberry bushes, which means without smurfberries he cannot make any juice. Fortunately Papa Smurf is mixing up an enlarging formula that would make little clouds into big rain clouds. After seeing Papa Smurf complete the formula, Brainy decides to mix up a batch of the formula itself to make big smurfberries. However, in his rush to get the formula to the smurfberry bushes, Brainy trips and falls, dumping the enlarging formula on Hefty, who was resting at the bottom of Smurfberry Hill after he helped Smurfette clear out the rocks in her garden.
After he grows to about 50 apples tall, Hefty starts to panic and runs to find Papa Smurf, only to come across Brainy who finds out that the enlarging formula has been dumped on Hefty. But instead of helping Hefty find Papa Smurf to restore him to normal, Brainy encourages Hefty to see his new size as something he always wanted, doing things that no other Smurf could ever do. Hefty agrees with this and ultimately decides to pay a visit to Gargamel so he can capture him. The other Smurfs see this as reckless and decide that they're going to tell Papa Smurf about this.
Meanwhile, Gargamel, who is also suffering from the heat wave, sees Hefty approaching, though at his giant size he is still about half the size of his enemy. Nevertheless, after hearing that Hefty is going to take Gargamel to the village as his prisoner, the evil wizard has Hefty carry him and his cat Azrael in a big sack so they could surprise Hefty and the Smurfs when they get there.
Soon, with Hefty appearing in the village with his captives, Gargamel turns the tables on Hefty and captures him as well as the other Smurfs. Papa Smurf, who was informed of what happened to Hefty, has the Smurfs lure Azrael around the village until Papa Smurf has him right at the spot where he dumps the enlarging formula on the cat, causing him to grow until he is as big as Gargamel. The evil wizard sees his now-big cat coming after him and gives up collecting the Smurfs to run for his life. After Papa Smurf restores Hefty to his normal size, he punishes Brainy for his actions by having him clean up the village.
Tropes associated with this episode include
- All Webbed Up: Papa Smurf by the spider that he accidentally made big.
- Attack Of The 50 Apples Tall Whatever: Hefty in this episode.
- Chase Scene: Gargamel gets chased off back to his hovel by a gigantic Azrael. Brainy also qualifies when he gets chased away by his fellow Smurfs in anger, after he asks Papa Smurf to make another 'magic potion' to clean up the village.
- Giant Spiders: Papa Smurf accidentally created one with his enlarging formula.
- Heat Wave
- It's All My Fault: Brainy confesses that the whole thing of turning Hefty big was all his fault when Hefty goes off to capture Gargamel and bring him to the village.
- Play-Along Prisoner: Gargamel and Azrael as they were taken to the Smurf Village by Hefty.
- Rage Breaking Point: At the end of the episode, the other Smurfs get mad at Brainy for mentioning about a magic potion and began to chase him around the village.
