The Laughing is the second part of the 23rd episode in Season 2 of Dexter's Laboratory, which first aired on January 21, 1998. In this episode, Dexter gets bitten by a pair of clown dentures during Dee Dee's birthday party, which causes him to turn into a clown at night and go terrorizing the town. This forces Dee Dee, with mime knowledge, to stop him.
The episode begins as Dee Dee bikes up to her house talking about why she has to go do things on her birthday. She goes to the fence door and everyone jumped up and yelled "Surprise!"; Dee Dee realized that everyone threw a surprise birthday party for her. When they're eating cake, Mom announced that the clown is here. He starts goofing around and tells an old joke. ("Why is 6 afraid of 7?"; "Cause 7 ate 9!") Everyone laughs except Dexter. The clown trips on a rock and his dentures shoot out of his mouth and sink deep into Dexter's arm. The clown apologizes, later, the family was having dinner. Dee Dee repeated the old joke, Mom and Dad laughed, then Dexter laughed in a funny way. He goes up to his room and transforms into a clown.
He goes into the city and creates chaos, he even stopped a date between a French-accented man and woman. The next day, Dexter wakes up and sees Dee Dee in his room and that his bedroom his covered with balloons. Dee Dee tells Dexter that he doesn't remember and shows him a newspaper headline which says "Crazy Clown lose in town." Dexter reads the newspaper but he doesn't recognize that the clown is himself. Dee Dee tries to prove to Dexter that he is the clown by taking a tracing paper on the clown picture and drawing Dexter's picture on it, but he has already gone into the lab and makes an antidote for his arm; but it isn't ready yet.
He watches 2 robots bump into each other and again starts laughing uncontrollably and turning into the clown once again. He goes out and causes a traffic jam and car crashes. A policeman needs backup. Dee Dee goes to a mime school where everything is completely quiet, she yells out for help and all of the mimes cover their ears. A mime teaches her how to witness the power of mimes. When they were done, the mimes give Dee Dee a uniform and she lets out a loud thank you; the mimes again covered their ears. Outside, Dexter is in a rambunctious chase with policemen and a dog. Out of nowhere, Dee Dee shows up, dressed as a mime, captures Dexter, takes him to the lab and cured him. Despite Dee Dee saving the day, Dexter's ungrateful ego tells her that he would have saved himself eventually without her help. Dee Dee traps her ungrateful brother in a mime box.