Personally, I don't give a rat's crap about who goes first in a talk show. Anyone wants to make a case out that is simply putting their hands in turds.
As for Luke Perry, he's the title role character of Jeremiah on SCI-FI (yeah yeah, the crappy channel). He's also been on TV as an alum of Beverly Hills 90210 and a friend of Jason Priestley (another BH90210 alum), who recently is recovering from a nasty car crash on the race track. Say what you want of them, they're friends. Of course, he also starred in the movie version of Buffy with Kristy Swanson (soon to appear in a Playboy layout, not SMG).
That movie somehow inspired Joss Whedon to do the TV series, which features Alyson Hannigan playing a witch. BTW, I think she's dating that British fellow who portrayed Wesley on Angel.