It's a Mad, Mad, Mad Hotel - S1-E12
Other mistake: In the episode "Its a Mad, Mad, Mad Hotel", when Esteban has his dream of becoming rich and London becoming his "Bell Girl", he calls the hotel "Hotel Esteban, but London's uniform still has a "T." When it cuts there is an "E" on the front desk.
Where in the World Is Pookie Stevens? - S3-E2
Other mistake: During the yard sale, in the first shot of Donnie's area where he has all his sports stuff, the sign behind him reads "Donny's Corner". "Donnie" is misspelled here. In all the shots after this one, there are sneakers, or some other equipment hanging over the "y's", hiding the spelling mistake.
Other mistake: Jane Webb is listed in the closing credits as "Store Lady". She actually played the "Story Lady". (00:25:00)
Other mistake: In the starting titles, the newspaper clippings state that Doogie sails through high-school in 9 weeks, the article says he is 12 years old. The next clipping says he graduates from Princeton at age 10.
Monkey Fun - S2-E13
Other mistake: Season 2 episode 13 "Monkey Fun": Just before the enlarged Titano appears at the zoo, there is a family watching normal-sized monkeys in a cage. The family father (farthest on the right) has a drawing disorder with his eyes: their pupils look up and down, respectively, giving him a rather goofy expression.
Injustice For All (2) - S1-E19
Other mistake: Unless he escaped prison, it makes no sense for Copperhead to be in the police van with the other Secret Society members. You can see him sitting there across from Solomon Grundy and The Shade.
Other mistake: A time card reads 6,000,002 BC, when it should've read "60,000,002 BC". (00:07:12)
Mona Lisa's Revenge (1) - S3-E10
Other mistake: Mr. Smith scans the Mona Lisa and determines that it is genuine from DaVinci's brush strokes. He should have also noticed the words "This is a fake" written in felt tip under the paint, from when The Doctor replaced the Mona Lisa with one of DaVinci's "forgeries" in "City of Death."
Other mistake: When Hudson is briefing the girls' football team he calls Mel Sarah, mixing up the character name (Mel) and actress (Sarah Lawrence).
Come Back, Little Googie - S1-E25
Other mistake: When Eddie's naughty little friend goes to shake hands with Herman they insert a quick close up of a hand buzzer in his hand, only it's obviously an adult's wrinkly hand.
Other mistake: In the scene where Yakko, Wakko and Dot are sitting at their desks repeating Miss Flamiel's every word, Wakko is drawn without legs (only feet) during one shot.
Other mistake: At the end of the intro, before the logo appears you can see Mojo Jojo's brain. His brain is green and it should be pink.
Other mistake: Misaki reminds Ishizaki about the next phase of the selection for the team. When he replies, someone drew eyelids on them, but the same color of the white of his eye. (00:02:30)
Other mistake: In the English dub of the series, Tai's last name is Kamiya; however, when he makes reference to the family name plate his father put on the front door in this episode, the name displayed is Yagami. (00:03:00)
Vampire Bats and Scaredy Cats - S2-E2
Other mistake: When the Mystery Company find a torn paper in a coffin, it is written exo-6 and something else. They find later that exo is the first part of exotic. The way the paper was torn, you should be able to see the lower part of the missing letters.
The Library - S3-E5
Other mistake: Dr. Mike spots a charred Bible within the charred piles of books, and heads into the church. The Reverend is giving a sermon on morality, and offers Dr. Mike the floor and she briefs about certain stories in the book, which would be considered scandalous, without mentioning the book's title, then hands it to the Reverend who agrees such stories are scandalous, until he turns it over, to see that its 'The Holy Bible'. Being a Reverend, he should know The Bible cover to cover, but reacts surprised or shocked over the mentioning of the scandalous stories. (00:36:00 - 00:41:00)
Coffee Quest/Phoenix Rises - S1-E18
Other mistake: In Phoenix Rises, when Phoenix runs away, the Big Coffee sign is missing.
Other mistake: When Viper slides the swords to Jackie and they come to a rest next to him, there is a small paper spider right beside Jackie. The only paper spider in the room, however, is Origami himself, and he is actually too far away at that moment and too big to fit the bill. Guess some of the animators got their depth perception messed up.
Dave and the Teenager - S11-E17
Other mistake: When the Harris family moves into an apartment across the hall from David and June Nelson, their 14-year-old daughter, Betty, develops a crush on David. When David and June step out onto their outdoor patio, they see Betty watching them from her own patio. This could not be possible.
Other mistake: When Uther takes Excaliber from Merlin while preparing for his duel with the black knight, we see that Uther is left handed. And he is left handed while writing. He tests the balance of the sword with his left hand, and in fact wears his sword on his right hip in all other episodes. Once he puts his helmet on and begins his duel with the black knight he suddenly becomes right handed.