Dexter to Melrose Place (2009)

Nina Batista on Dexter comments on her husband Angel's two Doublemeat burgers from Buffy's Doublemeat Palace.

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