Your Home Sweet Home is My Home Sweet Home - S4-E25
Continuity mistake: The Petrie house (where Rob and Laura, Jerry and Millie are standing together bickering) is completely different from the episode "Where Did I Come From?" and a few others.
Your Home Sweet Home is My Home Sweet Home - S4-E25
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.
Suggested correction: No, the Petries buy the house with the rock, but swap it with their best friends and buy the house next door. Therefore Jerry and Millie have the rock in the basement.
Rob has to pay half the cost for Jerry to seal his basement every year. The reason why is because Rob's rock redirects water that ends up flooding Jerry's basement.
The Petries did buy the house with the rock. At the end of the episode Rob explains how their rock caused flooding in the Helper's basement.