Castle to Millennium
4 connections
Castle
Law & Order
Hudson University from L&O also appears as the home of various victims and crimes in Castle,
Homicide: Life On The Street
Law and Order and Homicide crossed over on four episodes
The X-Files
Homicide's John Munch questioned The X-Files' The Lone Gunmen.
Millennium
The X-Files' Jose Chung was also investigated by Millennium's Frank Black and later X-Files' Mulder and Scully meet Millennium's Frank Black.