|Season Unknown, Episode Unknown|
|Written by||Chong Lee, Graig McCracken|
|Directed by||Rob Renzetti|
Last But Not Beast
Dexter builds a machine to make Dee Dee less rude, but Dee Dee argues him that he is the rude one. The argument breaks out into a fight and they both go into the machine which removes their rudeness and makes rude clones of them that go around cussing at their parents giving them the blame.
Dexter is putting the finishing touches on another one of his latest inventions. However, Dee Dee enters the lab and sees two tanks filled with gas and mischievously makes the gas explode in Dexter's hair. Dee Dee then asks what he's making, and Dexter explains it's called the Rude Removal system. He explains to her that he is going to use the machine to remove her rudeness and make her be more polite. Dee Dee denies this and retaliates back saying that he is the one who is rude. They then argued about who's rude and who's NOT! Dee Dee sarcastically replies that she is the rude one and kicks Dexter by the butt, causing Dexter to turn on the system. Dexter finally is able to tackle her, unfortunately this makes them both roll into the rude removal system, causing both of them to have their rudeness removed. After this happend, the two to have British accents and act more polite than before. This also however, creates two evil, rude duplicates of them both in the other end of the machine. The rude duplicates start cussing and beating up Dexter and Dee Dee and they run off cussing and destroying the lab.
Mom calls the two down for lunch, so the evil copies of Dexter and Dee Dee smash their way downstairs, breaking things and cursing. Just as they reach the dining room, they stop swearing and sit down at the table, they then proceed to shovel food in their mouths while making rude noises. Mom asks them how they're enjoying the meal, evil Dexter answers with a profane sentence, to which evil Dee Dee counters with more swearing, this makes Mom faint. When Mom awakens, she is caught between a food fight between the rude clones, further angering her and yelling at the two to go to their rooms "forever." In response to the request, Rude Dexter starts to back-talk Mom by telling her "to do what all good mothers do and clean up the mess yourself," then leaves the kitchen with Rude Dee-Dee. Rude Dexter spots Nice Dexter and Dee-Dee and tells their nice couterparts that their mother wanted them. They accept the matter and ask their evil clones where they were going, in which Rude Dexter replies, "Yeah, we're gonna go f**k up your lab!" The nice Dexter and Dee-Dee do not take the threat too seriously and go on to the kitchen where Mom equips Nice Dee-Dee with a mop and demands the clones to clean up the mess the rude counterparts made while she went out to get a bar of soap to "clean out" their mouths. When the nice counterparts are about to clean, they hear the rude clones destroying the lab, which lead their nice counterparts to stop their cleaning, leave a note for Mom and head to the lab before further destruction is made.
The normal Dexter and Dee Dee come to and are able to get their evil twins back to the lab, where they destroy them.The two then leave the lab as Dexter announces he was glad that there was no harm done, as they come around a corner, they see Mom standing before them menacingly with a bar of soap in her hand, she angrily calls Dexter and Dee Dee over to her, obviously intending to wash their mouths out with it. As Dexter looks into the camera, he says, "Ohhhhhhhh, s**t." before the iris wears out.
- This episode is famous for its excessive use of profanity.
- The episode contains two cultural stereotypes throughout the episode: Rude Dexter and Dee Dee have New York City accents and Nice Dexter and Nice Dee Dee have English accents.
- This is the only episode of Dexter's Lab to become an internet meme.
- It is rumored that this episode was once accidentally aired on Cartoon Network but these rumors would seem unlikely, because if it did air on TV once, the word about the episode would have gotten out sooner.
- Before the episode was released to the public, there were roumors that in this episode, one of the swears was going to be "Skull f**king d**chebag." However, this was never seen anywhere in the episode so it must have only been a myth.
- This episode is similar to "Curses" from The Powerpuff Girls, "The Word of the Day" from Rugrats, "To Bleep or Not to Bleep" from Tiny Toon Adventures, "Bleep" from Arthur, "The Bad Word" from Yoko! Jakamototo! Toto!, "Who Said That?" from Baby Looney Tunes, "DinglieDanglieDoodle" from Rolie Polie Olie, "Caillou's Crossword" from Caillou and "Sailor Mouth" from SpongeBob SquarePants.
- This episode is also similar to the Kung Fu Panda: Legends of Awesomeness episode "Bad Po".
- When Bad Dexter get's the pie, the cherry was red. But when Mom yells at him, the cherry went purple/black.
- At the beginning Dee Dee asks Dexter if he's going to make another remote control that turns people into animals, this is a reference to the pilot episode "Changes."
- The same sound that is made when Rude Dexter and Rude Dee Dee are first introduced, is heard in the episode "That Crazy Robot".