The Borgified Corpse wrote:
That problem crops up all the time. Similarly, we've seen episodes of The X-Files where The Simpsons is on in the background. Yet Mulder & Scully were once on The Simpsons. Also, there was a Mad About You episode in which we learned that Kramer from Seinfeld moved into Paul's old apartment. And yet, in Seinfeld, there are references to Mad About You as a TV show.
The movie SWAT is based on the TV show SWAT and the characters are the same ones from the TV show. Yet they also know the SWAT theme song and one of them was even watching the old TV series.
I'm still waiting for the ultimate CBS crossover where a storyline goes through every single one of their crime dramas -- Cold Case, CSI: Miami, NCIS, The Mentalist, Without a Trace, Criminal Minds, CSI: NY, CSI, Flashpoint and Numbers.
Maybe you could even throw in The Unit and Ghost Whisperer.