Part of the action in The Worst Thing Ever? is set in a school. Newsround used a REAL school for these scenes and some of the pupils got to appear in the programme.
Eleven-year-old Jeremiah landed a top role. He played the part of a boy who gets upset and is comforted by Darren - the main character in The Worst Thing Ever?
Here's Jeremiah filming a scene with Peter - who plays Darren in The Worst Thing Ever?
Kris, nine, was filmed running down a corridor: "We had to do it about three times to get it right. It was great when they shouted 'ACTION'."
Hannah, nine, said: "I was really excited but a bit nervous too. It was really hard not to look at the camera!"
The school looked VERY different as the crew and all their equipment moved in for the day.
Christina, nine, thought it was "really cool" having the crew in school. She told all her family and friends to watch out for The Worst Thing Ever? on television.
Nine-year-old Latifah also said she was really looking forward to seeing the final programme on television.
Callum, 11, was chosen to appear in a fireworks night scene: "We had to do the sparklers again and again - they kept going out too quickly for them to film!"