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
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.
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.