The Kiss Seen Around the World - S3-E8
Corrected entry: When Peter pretends to play the keyboard in the toy store, a man takes exception to it. When the Griffins are back in the parking lot, the man has spray painted the word "Phony" on their station wagon. The man just met Peter two minutes earlier, how would he know which vehicle to spray paint? (00:01:20 - 00:02:15)
Correction: If you watch the very first episode (I Never Met the Dead Man) you can see the phony guy, working on a new toy at the toy factory, where Peter also works. So they probably know each other from work.