The One With Chandler's Dad - S7-E22
Revealing mistake: In the shot of the highway with Ross and Rachel in the Porsche before the police officer walks to them, it is very obvious that the people inside the car are not actually them.
The One With Chandler's Dad - S7-E22
Revealing mistake: When we first see the Porsche, there are smear marks on the bonnet from previous takes of Ross diving across it. (00:04:35)
The One With Chandler's Dad - S7-E22
Revealing mistake: The number (licence) plate on the Porsche changes between the time it is outside the coffee shop (YSO 791) and the time Rachel and Ross are driving on the highway (JGL 334). (00:04:35 - 00:13:00)
Answer: These are references to the TV show NYPD Blue. Deputy Andy Sipowicz is the name of one of the characters, whilst another character (Deputy Danny Sorenso) is played by Rick Schroder who previously starred in the show Silver Spoons.
pinkwafer