Pingu's Dangerous Joke is the thirteenth episode of Season 4.
Today, Pingu is in a very mischievous mood. First he throws a snowball at the doorbell of a sleeping penguin's igloo. Then he decides to play a joke on Grandpa, who is going out to a site of abandoned igloos to collect some old bits of wood. As Grandpa picks up the wood and places it into the crate on his sledge, Pingu hides amongst the ruined igloos, watching him very carefully. Then whilst Grandpa's back is turned, Pingu comes out from his hiding and tips up the crate, spilling the wood all over the ground. When Grandpa returns, he is very puzzled about what happened to his wood. He looks all around to see who knocked over his crate, but there is no one to be seen.
Grandpa stops in front of a hillock of snow, not knowing that Pingu is know right above him. Next to Pingu is a large boulder on the edge of the hillock, which is being held dangerously in place by a small block of ice. Pingu decides to give Grandpa another surprise by removing the small block of ice and dropping it to the ground in front of him. Grandpa looks all around him to see where the block came from, but he cannot see anyone, so he just tucks into his fish sandwich for lunch. Then suddenly, with nothing to hold it in place, the boulder rolls away down the side of the hillock. Pingu is shocked and shouts urgently to Grandpa, who runs away just in time, dropping his sandwich in the process. The boulder reaches the bottom of the hillock with a thud and squashes Grandpa's sandwich flat.
Pingu slides miserably down from the top of the hillock and Grandpa, now realising what was happening, sternly tells him how dangerous his joke was as he could have seriously harmed him had he not told him sooner. Pingu guiltily tells Grandpa he is very sorry with tears trickling down his face. Grandpa is very glad that Pingu has learnt his lesson and the young penguin collects up the wood he knocked over and puts it back into the crate on the sledge. Once the sledge is loaded up, Grandpa and Pingu take the wood back home, with Grandpa pulling the sledge from the front and Pingu pushing at the back.
- Grandpa could have easily seen Pingu when he dropped the block of ice in front of him.
- After Grandpa's sandwich is flatten by the boulder, it suddenly seems to have become massive and papery.