Firefly to Veronica Mars
4 connections
Firefly
Angel
Weyland-Utani is a client of Angel's Wolfram & Hart and also the company that made some of the weapons used by Firefly's Malcolm Reynolds in the Battle of Serenity
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.
Veronica Mars
The mugshot of Malcolm T Wiggins from the X-Files episode "Titonus" appears on the wall of a police interrogation room in the Veronica Mars episode "Leave it to Beaver." Also the fictional car rental company Lariat where Mulder & Scully always rented their cars was featured prominently on the Veronica Mars episode "Rat Saw God."