Doctor Who (1963) to Melrose Place (2009)

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"

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.

Angel was a spin-off of Buffy the Vampire Slayer.

The X-Files? Cigarette Smoking Man and Buffy the Vampire Slayer's Spike both smoked Morley cigarettes.

Brenda Walsh picks up a Morley smoking habit while in Paris on Beverly Hills 90210

90210 was a continuation of Beverly Hills 90210 years later

Melrose Place (2009) was a continuation of Melrose Place which was a spin off of Beverly Hills 90210 that was continued as 90210