Doo Dee was a villian in the animated TV series Dexter's Laboratory, and the main antagonist in the episode Oh Brother. He is the male counterpart of Dexter's sister Dee Dee.
Fed up with Dee Dee trashing his laboratory once again, Dexter decides that life would be better if he had a brother that would share science with him. So he calls Dee Dee back in the lab and use one of his inventions and switches her gender from a female to a male. After using the machine, Dexter opens it but the machine is empty. The next morning, Mom calls Dexter and his "brother" to breakfast. Upon hearing the word brother, Dexter realizes that his test has worked. So he went to his new brother's room and saw that Dee Dee's room has been altered. When he went in, Dexter saw that Dee Dee is now Doo Dee his older brother. Much to Dexter's disgrace, Doo Dee only is interested in sports and is a jock. He also gives Dexter a noogie and uses him as a football. At breakfast, Mom and Dad begins to give all the food to Doo Dee and of course ignoring Dexter. They also spent time with each other by playing football. Dexter becomes crestfallen and goes to go work in his laboratory, but Doo Dee gets in and trashes the lab while using Dexter as a football again.
After this destruction, Dexter decides that having a brother wasn't exactly as much fun as he thought it would be. So he decides to bring Dee Dee back. He first lures Doo Dee back in the machine with his football and activates it. Doo Dee is changed back to Dee Dee and all is well.
"Hey, Dexter!"- First Quote