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.
Continuity mistake: The package Steve received from Mailbox is briefly visible before Mailbox comes in. You can also see a crew member's hand holding the package as Steve grabs it.
A Case of Overexposure - S5-E8
Continuity mistake: In season one episode 16, Arnold says that him and Willis never met their landlord. In this episode they remember him as Mr Darcy - when they see him they recognise who he is.
The Fall Guy - S1-E4
Character mistake: Thorny tells Ozzie that Clara Randolph is throwing a party. When Ozzie tells David and Ricky about that party, he calls her "Mary Randolph."
Emergency Marineville - S1-E11
Continuity mistake: When the second group of Spearhead jets take off from Marineville there are only two jets, but in the next shot you can see three jets, and in the next shot there are two again.
Continuity mistake: When Tsubasa is staring at the soccer grounds sign, it is written with a different layout in different shots. (00:10:10)
Continuity mistake: When Dum-Dum cuts the rope releasing Chug-a-Boom from the balloon, we cut to the car and you can see Clyde and Dum-Dum are surrounded by the rest of the Ant Hill Mob, but when we see the two in the next shot, the other members are nowhere to be seen.
Visible crew/equipment: Series 19, "Pandamonium": When Paul and Barry are trying to find the panda, Barry (dressed in a panda costume) thinks he is looking at his own reflection. You can see the camera and cameraman reflected in the mirrors, and you can also see people watching the scene being filmed.
El traje del tío Jacinto - S2-E16
Visible crew/equipment: In the credits, there's a unknown person hiding behind Don Ramón (Raymond).
Triumvirate of Terror! - S3-E8
Continuity mistake: Lex busts through the glass doors in S.T.A.R. Laboratory and the glass falls to the ground. In the wide shot, it is yellow. But in the close up of Lex's feet, the glass is suddenly clear. There is also more of it in the close up. (00:05:35)
A Single Piece Was Lost - S1-E10
Visible crew/equipment: When the Gruenaks attack the Scientist a puppeteer is visible to the right of one of the Gruenaks, just before it grabs the bird cage and throws it onto the Scientist's head. (00:28:18)
Flipper and the Bounty - S2-E13
Visible crew/equipment: After Bud wakes up all alone in Bligh's cabin, he soon realises all the doors are locked. Then, just as Bud rushes over to the stern window (particularly the second time), a seated crew member is visible at the bottom right corner of the screen; we can see the movement of a leg and two hands (so, it's not a mannequin).
Audio problem: Billie says her line "he needs a new image" without moving her lips.
Spider's Little Daddy/Tricycle of Terror - S3-E1
Continuity mistake: Mandy's working on her report. The page she's on says "CORN by Mandy." A moment later, she writes the same title on another page.
Revealing mistake: Patty Duke's stand-in is visible behind Cathy when the family is in the front hall welcoming their aunt.
Deliberate mistake: Season 2, episode 6 "Identity Crisis": When Bizarro starts decaying into the parody form of Superman, his costume goes with it; the blue fades, and even the 'S' insignia changes. Strange that superhero garments change right alongside their wearers when they suffer from an unstable genetic effect. Were the clothes cloned right onto his body, instead of sewn?
Continuity mistake: Before Charlie says to Lola "You must double-triple promise you'll never play with it", he places the rocket beside a black box. Later in the episode, when Lola attempts to get the rocket down to play with it, the rocket is now on top of the black box.
Continuity mistake: When Janet gets off the phone with Clarissa's principal, Clarissa is standing on the right side of her friend. The shot changes and she is now on the left.
Factual error: Bessie says she was going to study veterinary medicine at Texas A and M. That would have been approximately 1940. Neither women nor people of colour were admitted to TAMU until 1963 so she could not have even been able to apply.
Wind Chimes - S1-E9
Visible crew/equipment: In the scene where Mcduff and Johnson are trying to find water since it's extremely hot, they go Under The Bed and notice Alfred under there. Look in the background, for just a split second, you can a man walk past the from the door. It's for only a split second so it's quite easy to miss. (00:06:05)