2Geniuses 2Gether 4Ever is the third part of the 13th and final episode in season 4 in Dexter's Laboratory. The episode aired on September 5, 2003. In this episode, Dexter and Mandark as they both work together in their lab, but Dexter finds himself handling more than he can work with.
Mandark is in his laboratory when he gets a phone call from Dexter. Dexter tells him that he has finally given up on trying to stop him from destroying his lab and that he is deciding to give up his lab to him to make him more powerful so that he can take over the world. Mandark is shocked by this and thinks that this is a joke at first, but then he detects no lies and agrees to take his lab. Mandark goes over there and he keeps on thinking that Dexter is trying to pull a trick on him but every single time, it just seems to be something normal.
Dexter shows Mandark around his laboratory and shows him all of his amazing inventions and says that it probably isn't all that important to him because he has it all in his lab already. Mandark doesn't really have that in his lab because he is not as smart as Dexter so he has a nervous face and lies saying that he does. Dexter gives him the map of his laboratory and asks what he'd like to see first. Mandark says top secret plans and they go and see one of his plans which is a machine that makes people smarter. Dexter is about to use it on Mandark but he thinks of it as a trap. So Mandark puts Dexter in the trap and uses it on him. To his surprise, it actually works and it makes Dexter's brain huge and he becomes smarter.
After a while, Mandark realizes that Dexter is not pulling any tricks on him. He has finally given up on trying to stop him and he is now going to allow him to be evil and he is going to team up with him to help him with his evil plans for world domination. Mandark says that they can work together to build a machine that will help him take over the universe. He had already had the perfect plans for an unstoppable machine to do so, but he has never been able to build it because he doesn't have the technology and material. Dexter says that he has it and that he will be able to help him build it. Instead of helping Dexter however, Mandark makes Dexter do all the work while he sits back and does nothing. Dexter works for hours until he finally finishes it at the end of the day. Dexter gives Mandark the remote to activate the machine. Mandark tries pressing the button but it doesn't work, he tries it again a bunch of times and it's not working. Then, Dexter plus the machine in and the machine makes the title of the show Dexter's Laboratory. The blast makes Mandark fall over the way Dexter does in the theme song. This mean that Dexter did not build the world domination machine, he built the machine from the theme song. Dexter has now won his show back. He is about to make the rest of the episode be all about him, but just then the words THE END appear on screen because the episode is over.
Mandark was trying to activate a machine by pressing a button on a remote but it didn't work until Dexter plugged in the machine which made Dexter's Laboratory appear in green letter the way it does in the theme song, this was a reference to the theme song.
Dexter made a fourth wall joke when he said "Well, like I always say, if you can't play with the big dogs, stay on the porch." and the words THE END appear on screen and he says "Hey! What's this going on? I'm trying to wax poetic here!"
The Alien on the screen of the Alien Communicator Dexter has is the same alien from the episode of The Powerpuff Girls, called "Beat your Greens."
Mandark implies that he does not have all the stuff that Dexter had in his laboratory, but one of the things he mentioned was a giant robot which Mandark has been seen having multiple times in the series.
It was the last time when Dexter is not in his lab in a previous episode "Comedy of Feathers", even though Mandark has taken over the show and made three of the episodes about him.
The reason Dexter appeared in this episode before the episode "Comedy of Feathers" was possibly because of the episodes being aired out of production order.