Angel to Millennium
3 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.
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.