Visible crew/equipment: After Jack talks to Larry about the magazine quiz Jack asks Janet if anything's been bothering her, and just as Terri walks out of the kitchen holding the two cans, a crew member's hand can be seen behind Terri placing a bag on the counter. (00:04:15)Super Grover
Continuity mistake: After Jack brings the puppy over to the girls, the box he brought the puppy in was placed on the back end of their couch. At one point, it is knocked over, and you can see it falling down to the floor (past Janet). In a few shots, it's back on the table, and none of the characters were in a position to pick it up to place it back there.
Continuity mistake: Larry gives Cindy and Janet gifts to thank them for letting him live with them, so Janet gives him a kiss. However, three seasons later in the episode "Friends and Lovers," Janet kisses Larry at her wedding to which Larry says "Janet, that's the first time you've ever kissed me."
Continuity mistake: When Mr. Roper tries to explain to the girls and his wife what he was doing in Jack's bedroom, watch over Mr. Roper's left shoulder on the shelf. The number of yellow cans on the shelf keep alternating between one and two cans throughout several minutes.
Plot hole: Chrissy's policeman cousin informs the roommates that there was a complaint from a neighbor about her husband on his roof watching the girls dance in The Apartment with binoculars. However, when the girls were dancing, the front door was fully closed and the very thick drapes were fully closed so how could such a complaint exist?
Revealing mistake: During Jack's dance scene, the old lady that he dances with spins away from him and knocks off a man's toupee. The actress was supposed to knock it off as she went by, but it's obvious that she misses and instead quickly reaches over to snatch it off his head instead.ksc
Continuity mistake: While Jack is talking to the police officer about the missing rent money, they are standing in front of the TV set and the front door is open. When it cuts back to Jack and the officer, over Jack's shoulder the front door is closed, but when the officer turns to leave the door is open again.
Revealing mistake: In the episode "Out on a Limb", Jack leaves Terri in Mr. Townsend's office lobby to keep the secretary busy while Jack is supposed to climb a tree outside up to the window and move from window-to-window to get to Townsend's office. If you look at the window behind Terri and the secretary, you'll see Jack magically walk through the brick wall to get set up for the tree climbing scene.CLondon
Visible crew/equipment: In the episode "A Camping We Will Go", when Lana and Mr. Furley show up to the Cabin unexpectedly, watch closely when Lana tries to sit next to Jack on the couch.if you look through the window by the flag hanging on the wall you'll see Larry's girl, Laura, waiting outside by the front door (in her bright pink outfit) waiting to make her entrance.CLondon
Character mistake: Maria (Felipe's cousin) supposedly didn't understand any English (only single words like "yes") and would answer (in Spanish) "Que?" after a full sentence of English was spoken to her. However, in front of Jack, one of the girls said to Maria "Tell Jack the new English word you just learned" and Maria understandingly responded "No." There's no way that Maria could respond correctly to that question since she didn't understand any other English sentences throughout the episode.
Other mistake: After Jack leaves The Apartment with Mr Angelino, Janet and Terri are sitting on the couch trying to figure out a way to get money for Jack. When Janet gets up you can see the bathroom door start to open behind her but there is no one else in The Apartment to open it.Bill39568
Other mistake: In the Regal Beagle, Jack addresses Marsha as Ms. White although later in the episode her last name is revealed to be Whitewood. In addition, how could Jack have known her last name anyway? Marsha only said her first name in front of Furley and the trio early in the episode and presumably she hasn't talked to the trio since she left with Furley out the door.