Californication to The Hitchhiker's Guide to the Galaxy
6 connections
Californication
The X-Files
Morleys
Buffy the Vampire Slayer
The X-Files? Cigarette Smoking Man and Buffy the Vampire Slayer's Spike both smoked Morley cigarettes.
Angel
Angel was a spin-off of Buffy the Vampire Slayer
Red Dwarf
In the Red Dwarf episode "Psirens", the crew of the Red Dwarf come across a space ship graveyard which includes a Weyland-Utani ship, connecting it with Angel.
Doctor Who (1963)
The TARDIS from Doctor Who appears in the hangar bay of the Red Dwarf - it can be seen during the launch of Starbug in the episode "Thanks for the Memory"
The Hitchhiker's Guide to the Galaxy
The Tenth Doctor mentions knowing Arthur Dent of Hitchhiker's Guide to the Galaxy.