Beverly Hills 90210 to Deadline

Brenda Walsh picks up a Morley smoking habit while in Paris on Beverly Hills 90210

Homicide's John Munch questioned The X-Files' The Lone Gunmen.

Law and Order and Homicide crossed over on four episodes

Characters from various Law & Order series have read, referenced or visited the offices of the New York Ledger, the fictional paper from Dick Wolf's series, Deadline.