Mitch Pileggi by Sergei Bachlakov/The CW Mitch Pileggi by Sergei Bachlakov/The CW

It's the hour that might drop the collective jaw of Supernatural fans who think they have the CW series' mythology all figured out. "In the Beginning," airing this Thursday at 9 pm/ET, guest-stars Mitch Pileggi as Samuel Campbell, the Winchester boys' maternal grandfather. The Back to the Future-esque tale finds Dean face-to-face with not only Gramps but also his would-be parents, as light is shed on the dark truth about That Night. TVGuide.com invited Pileggi to preview his visit, reflect on his least-appreciated TV role, and ponder the prospects for X-Files 3. - Matt Mitovich

TVGuide.com: How did the Supernatural opportunity come to you? Was it a case of someone knowing someone who knows you...?
Mitch Pileggi:
I had worked with [ Supernatural creator] Eric Kripke on another series ( Tarzan) some years ago. He told me he had been looking for something for me to do on the show, but he wanted to wait for the right role. This came up, they called me, and there was no hesitation.

TVGuide.com: You often seem drawn to anthology-type series. Do you feel it's a smarter, more involved genre of television?
Pileggi:
This show is definitely smart. but honestly, what draws me to any show that I do, these days especially, is if the role is something that is going to challenge me, that is interesting to me, and is something I haven't played before. The main thing that drew me to this was the fact that the people working on it, from the crew and production, are people I worked with on The X-Files. I had a lot of "old family" working on the show. When they sent me a couple episodes, I actually called Eric and said, "Why have I not been watching this show?!" I think it's really good, and the guys on it are wonderful. It's a great cast, great stories, and it looks absolutely wonderful.

TVGuide.com: You and Jensen Ackles have a very tense face-off at one point. Is that a scene you rehearsed and he knew exactly what you would be throwing at him, or was there some element of surprise to your performance?
Pileggi:
He had no idea what I was going to be doing until I did it. It was... fun, man. [ Laughs] To be quite honest, I didn't know what I was going to be doing. It kind of just "happened." Usually when I don't know what I'm doing is when I'm the happiest with it.

TVGuide.com: Amy Gumenick, who plays your "daughter," Mary - this was her first big acting job? I thought she was pretty darn good, and had great screen presence.
Pileggi:
She was wonderful. Absolutely wonderful. I had a good time working with her. It turns out she went to school and was taught by a very good friend of mine, Sage Parker, who is Mary-Louise Parker's sister.

TVGuide.com: Which of your past TV series would you say most didn't get its due?
Pileggi:
Probably Day Break....

TVGuide.com: An awesome show.
Pileggi:
People just don't have the attention spans to really watch something like that. It was a show you had to really pay attention to, and I think the audience was not up for that. It's frustrating, because that show was a lot of fun and the cast, we were having a good time. And then it's gone.

TVGuide.com: What lies ahead for Colonel Caldwell during this final season of Stargate Atlantis?
Pileggi:
I just got done doing the final episode, and I'm still flying around the Daedelus. I'm just a cab driver. [ Laughs] Just more space battles and saving Sheppard and the others.

TVGuide.com: You popped up on Brothers & Sisters this week, as Kevin's boss.
Pileggi:
Yeah, and I did two more episodes after that. It was a last-minute deal. They had lost somebody and called me the night before, so.... I'm their "hired gun."

TVGuide.com: Do you think Chris Carter has another X-Files movie in him?
Pileggi:
[ Defeated] I don't know.... Do you [think so]?

TVGuide.com: I... think that I Want to Believe's lackluster box-office performance may have sent that ship sailing.
Pileggi:
OK. I'll let you say that.

TVGuide.com: Have you heard at all from David Duchovny? Is he doing OK? [Duchovny sought treatment last month for sex addiction.]
Pileggi:
We don't really communicate. But I hope he's doing OK. I'm sure he'll be fine.