While Dexter is a boy genius, one needs to keep in mind that he's still a child and thus is very capable of making mistakes.
- In "Maternal Combat", Dexter's mom falls ill. Dexter doesn't like this, especially when Dee Dee tries to cook in their mom's place.
You'd Expect: He would invent a cure for whatever has laid her down so she can get back to being a mom.
Instead: He builds a mom robot, complete with a remote control.
The Result: Dee Dee gets her hands on the remote, and Hilarity Ensues. By the end of it they've damaged the house from a mom robot fight. - In "Germ Warfare" Dee Dee, who is sick with the flu, enters Dexter's lab in order to find her hanky. Dexter is in a protection bubble and is worried that Deedee will spread her germs.
You'd Expect: Dexter to still tell Dee Dee to stay out, but to add that he'll search her hanky for her and then do so, or give her another hanky or paper tissues.
Or: Him to try to cure her.
Instead: All that he does is yell at Deedee to leave with her germs, and while he has a point, he never thinks about any of the options mentioned above.
The Result: Dee Dee continues her search for her hanky, infesting the lab even further, then she inhales the fumes of some chemicals and starts sneezing fire, burning the lab down. Dexter tries to reach for a fire extinguisher, and is of course blocked by his bubble. Then Dee Dee sneezes at Dexter's most recent invention, destroying it and Dexter's bubble, causing Dexter to catch her illness in the process. - In "Trapped With a Vengeance", Dexter constantly stays at the school past designated hours and makes a mess out of the school after Yani the janitor has already cleaned up forcing Yani to clean up the mess he made before he can return home where his wife is angry at him for arriving so late.
You'd expect: Being an adult, Yani would report Dexter for staying past school hours when he should be home and forcing Yani to work overtime, giving Dexter the appropriate punishment and most likely preventing him from making any more messes.
Or: Him to try talking things out with Dexter. He could ask Dexter to find another place to make his experiments in the evening and maybe suggest a possible place. The janitor could also threaten Dexter with the option mentioned above if the latter doesn't cooperate.
Instead: He prevents Dexter from leaving the school when Dexter prepares to leave and tries to make sure he can't escape.
The End Result: In all of his efforts to keep Dexter from leaving the school, he ends up making a complete mess out of the cafeteria while taunting Dexter; his wife also shows up angry about him not coming home, and Dexter gets to go home scott free.
What's Worse: He doesn't even get to clean up the mess he had made before leaving, so not only does he get his wife angry at him again, but he more than likely got fired the next morning for not cleaning the school, which would explain why he only appears in this episode. - In "Dexter Detention," Dexter is attempting to finish a test, only for a Jerkass student to bother Dexter and constantly ask for the answer to a question.
You'd Expect: For Dexter to pause his test and complain to the teacher about the student pestering him. It also helps that the student is also attempting to cheat.
Instead: Dexter loses his patience and accidentally blurts out the answer, causing him to go to detention. Plus, the other student gets away with bothering Dexter. - "Dexter vs. Santa's Claws," widely considered the show's worst episode, is a glaring example of how Dexter's ego can lead to him holding the Jerkass Ball.
- On Christmas Eve, Dee Dee writes a wish list to Santa Claus on Dexter's computer. Dexter mocks Dee Dee, telling her he doesn't believe in Santa and —through a bad rap song— tells her that it's just their parents dressing up as Santa and a reindeer, decorating their car like a sleigh, and putting the presents around the tree. Likewise, Dee Dee immediately tells Dexter that his theory is bonkers and that Santa indeed exists. To prove his theory right and protect his ego, Dexter decides to hold a stakeout in the living room to prove once and for all that there is no Santa. When Santa teleports into the room, it's clear to anyone that he looks absolutely nothing like Dexter's dad. It also doesn't help that he only speaks in "Ho ho ho"'s.
You'd Expect: For Dexter to tell the obvious differences between his dad and Santa, and come to the conclusion that his theory is wrong.
Instead: He denies the obvious and still thinks that Santa is his dad in disguise, leading to a fight between them. - On the rooftop, Dexter finds Santa's sleigh and a reindeer (both real). He talks to the reindeer as if it's his mom before ripping the antlers off of it.
You'd Expect: That Dexter would then get the message after pulling the very real antlers off the reindeer's head (not to mention that it looks too real to be a human in a costume), and then apologize to it and to Santa for assaulting them.
Instead: That doesn't happen at all. - Santa angrily shoves Dexter into the chimney and flies off. Note that nowhere in Dexter's theory did he say that his dad's car could fly, which means that his theory is already proven wrong.
You'd Expect: That with the discovery of a real Santa Claus (who clearly isn't his dad as established above), a real reindeer, and a real flying sleigh, Dexter would finally accept that his theory is wrong and go back inside.
Instead: Dexter somehow converts the chimney into a fighter plane and pursues Santa, destroying his sleigh (and a few presents) in the process. The sleigh crashes into the house, and Dexter viciously shaves off Santa's beard.
End Result: Dexter's dad walks in and scolds him, and only then, does Dexter finally break out of his delusion and realize that Dee Dee was right. The whole fiasco left the house in shambles, the Christmas tree burned up, the sleigh completely totaled, and the presents presumably destroyed. On top of that, Dexter tries to defend his actions with lame excuses that are easily broken down by Dee Dee. So Christmas is now effectively ruined for everyone because of Dexter's ego and temporary stupidity. So much for a heartfelt Christmas special ending that could have delighted us all. - Adding to the idiocy, throughout the episode until the end, Santa has the aforementioned problem with speaking in "Ho ho ho"'s.
You'd expect: At some point, Santa should've explained to Dexter in plain, simple English that he's the real Santa Claus and not Dexter's dad in disguise. Even if he didn't think Dexter would believe him, he could point things out like the fact that his reindeer is clearly real, his sleigh can fly, etc.
Instead: He never does this until the end.
The Result: Not only does the episode end like that, but then we find out he's capable of speaking English when he said that Christmas was about "presents", leaving it very confusing as to why he never spoke before then.
- On Christmas Eve, Dee Dee writes a wish list to Santa Claus on Dexter's computer. Dexter mocks Dee Dee, telling her he doesn't believe in Santa and —through a bad rap song— tells her that it's just their parents dressing up as Santa and a reindeer, decorating their car like a sleigh, and putting the presents around the tree. Likewise, Dee Dee immediately tells Dexter that his theory is bonkers and that Santa indeed exists. To prove his theory right and protect his ego, Dexter decides to hold a stakeout in the living room to prove once and for all that there is no Santa. When Santa teleports into the room, it's clear to anyone that he looks absolutely nothing like Dexter's dad. It also doesn't help that he only speaks in "Ho ho ho"'s.
- In "Sdrawkcab", Mom has asked Dexter to take a bag of rubbish to the garbage man (which he hates doing). Dexter is also wearing a belt that reverses his actions so he ends up not giving the bag to the garbage man and bringing it back into the house.
You'd expect: For Dexter to just simply leave the bag of rubbish where the garbage men can pick it up.
Alternatively: He would take the belt off so that he will be able to function normally.
Instead: He continues trying to hand it to the garbage man and eventually makes Mom angry with him for seemingly disobeying orders. - At the end of Misplaced In Space, Dexter is explaining to Dee-Dee how he ended up in the alien prison, pointing out how he'd been working on his transporter and then Dee-Dee entered the lab. He's in the transporter as well.
You'd expect: Dexter would move out of the transporter before finishing his explanation or that he wouldn't have entered it in the first place.
Instead: Dexter stays in the transporter while pointing at the button that Dee-Dee pressed which caused him to be transported into outer space.
Result: Dee-Dee presses said button and Dexter is presumably sent back to the alien prison.
