Angel to Castle
5 connections
Angel
Buffy the Vampire Slayer
Angel was a spin-off of Buffy the Vampire Slayer.
The X-Files
The X-Files? Cigarette Smoking Man and Buffy the Vampire Slayer's Spike both smoked Morley cigarettes.
Homicide: Life On The Street
Homicide's John Munch questioned The X-Files' The Lone Gunmen.
Law & Order
Law and Order and Homicide crossed over on four episodes
Castle
Hudson University from L&O also appears as the home of various victims and crimes in Castle,