Acording to...
http://blog.zap2it.com/frominsidethebox/2008/10/krumholtz-says.html
Penn is to make an appearence in a show called Numb3rs November 7th, I dunno what channel or time it's on.
From that article:-
"Along with Carradine, other guest stars include Lou Diamond Phillips (in the premiere, a story about rock climbing written by married show creators Cheryl Heuton and Nick Falacci, a climbing enthusiast), Henry Winkler and magician and professional skeptic Penn Jillette.
Jillette's episode, airing Nov. 7, has him in a cameo role as himself, helping in the case of a vanished magician. Apparently magic wasn't the only lure for Jillette.
"It's happening right now," Krumholtz says. "Penn is actually one of the die-hardest fans of the show I've ever met. He's seen every single episode. He's a very opinionated person, so it's good to be on his good side.
"He feels really strongly towards the show and was really into the idea of doing it. He's having a lot of fun.""
Cheers
Jamie
*The best song ever written goes G D A D.
You can figure out which one I mean.*