This man is essential to geeky television.
Every time I turn around he pops up on one of my shows.
The X-Files (Fire)
Sliders (Net Worth)
Star Trek: Voyager (Child's Play)
The Invisible Man (Diseased)
Charmed (Witches in Tights)
Murder, She Wrote: The Celtic Riddle
Monk (Mr. Monk vs. the Cobra)
Without a Trace (Requiem)
Plus, several other shows that don't really qualify as "one of my shows," but I have intentions of watching them (they're likely sitting in my Netflix queue waiting for me).
It's like it's not a legitimate sci-fi/fantasy/supernatural show until he shows up.