Happy Birthday! (Part One) is the 100th episode of Clarence and the second to last episode of the series. The plot revolves around Belson trying to ruin Clarence's party in various ways.
- Ms. Baker
The episode starts out at the end of class, and Clarence gives everyone invitations to his 10th birthday. Like in the first episode, Belson plays hacky-sack with Clarence's invite. The next day, Clarence and his mom have set up Clarence's 10th party. After everything is set up, a weird clown called Doofus the Clown (Joshua) arrives. He gets on the stage, burps out balloons, and then juggles them. Clarence claps and gets excited. Not soon after, kids start to arrive, including Belson. Sumo runs in, slides on the ground leaving a giant mud puddle. Finally, Jeff arrives and he sits down in the picnic chairs and talks to everyone's parents. Clarence goes and opens Reid's present, which is shampoo. Clarence looks disappointed, but Sumo says that they can have fun with it. Sumo takes the shampoo to the top of the waterslide, opens it, and gushes down. Sumo and Clarence slide down at the same time. The two boys fly off of the waterslide and land in a puddle of mud. Clarence and Sumo go to do it again. Then, Belson approaches Clarence and tells him to open his present. Clarence opens Belson's present, and it reveals that Belson got an Acadia Play Cube. Clarence opens it, but rocks come out. Belson starts laughing, and eventually falls over. Clarence surprisingly gets excited about the rocks, and then Belson gets mad. Clarence's mom then announces that it's cake time. Everyone goes to the table and eats a slice of cake. Belson doesn't eat his slice, and throws it at Clarence instead. The piece of cake missed and hit Jeff. Jeff gets mad, screams and asks Mary to give Belson a timeout. Mary ignores him. Jeff then goes inside to wash his face. Then, Belson jumps on the table and stomps the remains of the cake.