The Great Petrie Fortune - S5-E6
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).