To Tell or Not to Tell - S1-E8
Continuity mistake: In this episode Sally asks Rob if he has a brother, Rob says "Yes, but he is married." However his brother Stacy is trying to become engaged later in the series, in episodes "Stacy Petrie Part 1 and 2."
Continuity mistake: The "Staff Writers" door is backwards. In other episodes the door opens up to the right, not to the left. Also the door is a dark color normally, unlike this scene in this episode where it's a light color. (00:19:41)
Visible crew/equipment: While Rob is sick in bed he's just about to grab the phone near the end of this episode you can see a big shadow of a giant camera in between the back of the TV set and a stage light behind the camera. (00:21:22)
Other mistake: Laura tells Rob "oh you don't smoke!" But in several (double digit) episodes Rob not only has a lighter but also a cigarette in his hand or mouth. One episode while he and Laura are illegally about to eavesdrop he puts out the cigarette on the speaker causing the speaker to turn on and they start eavesdropping again.
Revealing mistake: When the female witness is called to the stand, VERY obvious shadowing of the boom mic when she stands up - you can see it on the wall.
Factual error: Talking to the lawyers, parties, or witnesses about anything. This will give the impression that something unfair is going on. And is also illegal. Which Rob was doing during this whole episode.
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)
Other mistake: Laura and Rob do not like having guns in the house and Laura is terrified about having them in the house... Yet in this episode... There are 2 guns in the basement displayed right next to a giant deer head on the Cross beam in the middle of the room up high. Neither of them care that the guns are there.
My Husband Is Not a Drunk - S2-E6
Other mistake: If Rob is that easily hypnotized then when Rob's friend hypnotized Millie he would have gone out light a light same when he did Laura and Jerry. Rob would have been out right then and there for all 3 of them... Not just when he did Buddy.
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.
What's in a Middle Name? - S2-E7
Deliberate mistake: Rob, Sally and Buddy's "old office" is exactly the same shape as Robs basement (except for the door in the center of the back wall. Instead of going upstairs it's all on 1 level. There's a door to the right which goes into a random room which we never get to see inside). (00:10:38)
Suggested correction: Since you listed multiple differences, it's obviously not "exactly the same." Filmmakers not building every set and prop from scratch is not a mistake. Modifying and reusing old sets is just an economic reality of production. If anything this should be under trivia.
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.
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.
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)
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.
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)
A Man's Teeth Are Not His Own - S2-E13
Factual error: Rob is in the middle of eating a sandwich. You can't break a tooth on a sandwich unless it's frozen, cement, glass or made of ice.
Suggested correction: Rob specifically said he broke the tooth on a chicken bone that was in the sandwich.
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)