Continuity mistake: In this episode it is shown that the Petries live in a house with a huge rock in the basement. In the episode where Buddy's brother, Blacky visits "Hustling the Hustler", they play pool in the basement and there is no rock.
Factual error: When Laura and Sally are about to go to the bedroom, Buddy and Rob are going to sleep in the living room of the haunted cabin. Rob and Laura tell Buddy and Sally things like how he steals the pillow and he takes all the covers at home. However at home, they sleep in twin beds so they shouldn't know such things. However, they do have a son. They had to share a bed at least once in their marriage.
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)
Other mistake: Evan from the insurance company comes over to ask Laura and Rob several questions but not once does he find out any names from the party. But the next day Buddy, Sally, Mel, Jerry and Millie all get really angry because of Rob and his interrogator just assuming that they stole the watch.
Plot hole: If Rob was just 12 or 13 when he last saw his grandfather (that's what they said in this episode, also he never called his grandfather ever from what it looks like) then his grandfather wouldn't know that he has been working on a TV program. (He started working on the Alan Brady show when he was 20, not before).
Stupidity: Rob tells Jerry "I haven't stopped sneezing long enough to take allergy pills" yet right after he says that, he doesn't sneeze anymore till he gives out his home address. He could have just taken his pills then. Someone behind the camera probably reminded him to continue sneezing. (00:16:52 - 00:18:00)
Factual error: Rob tells this lady that the guy that passed away was his great-uncle and that the last time he saw him was when Rob was 12 years old... This is the same Grandpa that was also seen in the episode "What's in a Middle Name" (in this episode in season 5 Richie would be 10 or 11. But the other episode he was supposedly 8).
Continuity mistake: In the 1st episode there are about 20 pictures behind the writers desk. Next episode... Gone, replaced with a giant bookshelf and a bunch of scripts. The bookshelf was behind the couch in the 1st episode.
Other mistake: The record that is to Rob's right (our left) isn't spinning while the base part under it is, until Rob puts the ceramic coffee cup on the record. Notice that ceramic coffee cup is also the same coffee cup that Rob threw away in the episode "Your Home Sweet Is My Home"
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)