Theo and the Kids (2) - S7-E26
Other mistake: After the commercial, when Olivia and her friend are watching TV, they look at each other and laugh, obviously on cue. They weren't even looking at the TV and started laughing at exactly the same time.
You Can Go Home Again - S7-E10
Other mistake: When Denise hangs up the phone after inquiring about the two bedroom apartment, actress Lisa Bonet's multiple tattoos are visible on the back of her neck and shoulder. In every other scene her tattoos are obscured with makeup as they wouldn't fit with Denise.
Chosen answer: That is the song "Open the Door Richard."