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. In addition, also notice the suitcase on the floor under the shelf as well. Whenever one yellow can is shown, the suitcase is by itself and whenever two yellow cans are shown, there is a square silver bag in front of the suitcase.
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.
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)
Character mistake: Janet is waiting for Larry to deliver her new car and states to Jack that this is her very first car. But 5 episodes earlier in S8-E13 "Itching for Trouble" when Moose asks if they had a football that needed air, Janet says no, but one of the tires on her car are low.
Continuity mistake: When Jack is on the phone explaining why he can't go into work again because he's really hiding at home from the bully Max, there is a chair wedged up against the front door. Larry knocks and when Jack is sure it is indeed Larry, he unlocks and opens the door without the chair in the way any more.
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.
Character mistake: In S5-E15 "In Like Larry", Larry gives Cindy and Janet gifts to thank them for letting him live with them, so Janet gives him a kiss. Larry also kisses both Janet and Terri on the lips at the end of S7-E6 "Opening Night" after showing them Greek dancing. However, in this episode Janet kisses Larry at her wedding, to which Larry says "Janet, that's the first time you've ever kissed me."
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: In Angelino's kitchen, when Mr. Angelino comes in and mentions steaks for eight people are needed, look behind him at the door's window. Janet is briefly seen watching (as if waiting for her cue to enter), then quickly ducks out of sight. A second later, she's seen again while Angelino asks Felipe to help him in the freezer. She then runs in the door with Furley as if they first arrived at that moment.
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.
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.
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.