May 12, 1996 (original) December 25, 1996 (re-airing)
Dexter's Rival is the first part of the third episode of season one of Dexter's Laboratory, which first aired on May 12, 1996. It later re-aired as the first part of episode 12 in season one on December 25, 1996.
In this episode, Dexter meets Mandark Astronomonov, who quickly turns out to be better than Dexter himself.
Dexter becomes arch enemies with a new student at the school named Mandark who appears to be smarter than him and steals his title of being the smartest kid in school.
It's the first day of school and Dexter is having a great time. All of the teachers and students are welcoming him back to school because he is their star student. A new student comes along named Mandark who is so much smarter than Dexter and the teachers love him more.
Dexter is crying over himself meeting his match. Mandark comes up to Dexter and tells him that he knows that he has a lab and he wants to see it. Dexter shows Mandark is lab thinking that this is the only thing Mandark doesn't have. Mandark is unimpressed and he shows him that he has his own lab. Dexter is shocked to learn Mandark has his own, much larger, lab and seems to be his intellectual superior. Dexter is faced then with two choices, which are becoming Mandark's lackey and shutting down his lab and discontinuing any further experiments here on in.
Dexter is forced shuts down his lab and discontinue any further experiments here on in... forever. Then he miserably goes to school the next day. All of the teachers and students now ignore him and they all love Mandark the way they used to love Dexter. Just then, Dee Dee came up to Dexter yelling, "Hi Dexter!" Mandark overhears this and when he sees Dee Dee he falls madly in love with her. He goes up to Dexter and asks about her. Dexter has the idea to set Dee Dee up with Mandark for a way to make him smarter.
Dexter leaves a trail of candy from Dee Dee's room to Mandark's house and Dee Dee follows it. When she gets to Mandark's house Mandark is waiting for her and he takes her into his lab. He wants to dance with her and when she hears that, she starts dancing all over the place like an idiot and she starts destroying everything in his lab. She completely destroys his entire lab and she leaves. Dexter is watching from his lab (with a root beer bottle for celebration) which he has reactivated up and continue any of his further experiments, so now he has been re-united with his one true love, which is his computer.