It May Look Like a Walnut! - S2-E20
Character mistake: Rob is having a nightmare, part of which involves the disappearance of his thumbs. When he finds Laura at home, the script calls for him to say, "I want you to help me get my thumbs back," but he actually says, "I want you to help me get my thumb backs." His thumbs are also still there but hidden (you can see a portion of them in one frame of the episode).
A Man's Teeth Are Not His Own - S2-E13
Revealing mistake: When Rob is "playing" the piano none of the keys on the piano look to actually be pushed down. Also when he's scratching his back with each of his hands the notes on that same side of the piano are still played. He's not actually playing the piano. (Except for the last 2 notes or chords). (00:02:46 - 00:03:27)
Continuity mistake: When Laura tries to read the phone number that Rob scratched out, Rob gives her the number as "New Rochelle 69970," which happens to be the Petrie's own phone number, as noted in other episodes.
Revealing mistake: Rob and Laura are both freaking out and panicking in their bedroom when all of a sudden Jerry shows up outside their closed window. Yet Jerry puts his arms in their room, showing it's not an actual window.
Continuity mistake: Rob, Laura, Buddy and Blacky are in Robs basement, there is no wine bar, or giant boulder, and the steps that come down from upstairs lead straight up to nowhere. Because there's a window to the left beside the steps, rather than how it was when they were buying the house where you could see into the house. And there's a giant gap under the wall behind the pool table. There's also a random door that leads somewhere also behind the pool table. (00:24:47)
What's in a Middle Name? - S2-E7
Other mistake: Laura tells Sally, Rob and the rest of the staff she's going to have a baby in a few days or so while she was at the Alan Brady Show. If Laura is going to have a baby she should have the baby bump the whole episode while she and Rob are reminiscing. (00:05:00)
Suggested correction: She says no such thing in that scene.
Deliberate mistake: Rob is about to leave his room, and he opens the bedroom door to the noise of a loud music box that was originally being made by Laura's music box that holds jewellery in it.
Audio problem: When Rob is yelling at the officer about the dining room set and saying "I want my dining room table and chairs!" you can hear a random bell tinkling away behind the camera. (00:17:50)
Will You Two Be My Wife? - S2-E17
Revealing mistake: While Rob is asking for 2 passes for 3 days in the Captain's office the plant that is outside the "closed window" behind the open blinds has leaves can be seen in between each of the blinds. Which means that the tree isn't actually outside and there is no window, just a window frame. (00:04:40)
It May Look Like a Walnut! - S2-E20
Continuity mistake: The episode opens with Rob watching a horror movie on television. The bedside clock shows the time as 9:05. At the end of the episode 23 minutes later, the clock shows 9:10.
Factual error: While Rob is roaming the house with a gun in his hand he chops the metal tube that the wood burning stove in the living-room is connected to. However since in real life the metal tube would be thick and insulated the tube he dented with his hand at that speed wouldn't have been damaged at all. Also, it could have broken his hand or at least sprained his hand where he wouldn't be able to use it or feel like using it.
What's in a Middle Name? - S2-E7
Other mistake: The desk that was Rob's Grandpa's in this episode was not the same exact desk that Rob inherits in "The Great Petrie Fortune" after his Grandpa passed away. (00:17:40)
Suggested correction: Rob inherited the desk from his great-uncle, i.e. his grandfather's brother.
What's in a Middle Name? - S2-E7
Other mistake: The piano in this episode in the Petries' old house behind Sam Petrie is the same piano from Rob's new office.
What's in a Middle Name? - S2-E7
Other mistake: Rob and Laura's old house changes from episode to episode when they go back in time reminiscing. 1: Petries and Helpers are in Rob's old house the size of that house was a trailer sized house. 2: Rob was in the Army the house was the size of a small apartment.
Factual error: Rob says to his doctor that they have catfish at his home yet you never see the catfish ever. The only time you see fish in this series is on a plate or in the episode "The Night the Roof Fell In" which weren't catfish. (00:11:33)
When a Bowling Pin Talks, Listen - S2-E32
Continuity mistake: Buddy poked the punching bag with Mel's face on it. Then later Mel comes in when the delivery service guy comes. Mel's face is aiming towards the wall. His face on the punching bag keeps appearing and disappearing every time we jump cut from the writers and the delivery guy.
A Bird in the Head Hurts - S2-E11
Revealing mistake: The problem with Rob's story is that he said he shot the bird with the rifle, but the rifle there that Rob is swinging around doesn't have a hole for bullets to come out of. It's a fake.
A Surprise Surprise Is a Surprise - S2-E30
Factual error: Buddy asked Sally "why haven't you had a birthday...?" Yet a few episodes ago (Season 1 Episode "Where you been, Fassbinder?") Sally had a birthday she cried and cried. Buddy and Pickles, Rob and Laura were all there.
Continuity mistake: When Rob is trying to draw the horse and accidentally draws on the wall, the drawing changes depending on the shot.
Other mistake: Richie has Rob's electric razor from Richie's bathroom. Rob and Laura have a bathroom for themselves... Rob doesn't need to put his stuff in Richie's bathroom.