‘Big Bang Theory’ Star Johnny Galecki Says Mark Hamill Has a Surprising ‘Roseanne’ Fixation (Video)

Actor also talks to TheWrap about CBS sitcom’s prospects beyond next year

“The Big Bang Theory” welcomes one of its biggest guest stars for Thursday’s season finale in none other than Luke Skywalker himself, Mark Hamill. But Johnny Galecki revealed that the “Star Wars” alum was far more interested in some “deep-ass trivia” regarding his “Roseanne” character, David Healy.

“[He] had a lot of questions, like old ‘Roseanne’ trivia questions,” the actor told TheWrap. Specifically, that his character was called Kevin, not David, in his very first appearance on “Roseanne.”

“That’s some deep-ass trivia, man,” Galecki remembers telling Hamill.

Overall, Galecki said Hamill was just excited to take his place among the “Big Bang Theory” gallery of geeky guest stars including Stan Lee, Stephen Hawking, Leonard Nimoy, LeVar Burton, George Takei and his “Star Wars” co-star, the late Carrie Fisher.

“He’s just incredibly effusive to be there,” Galecki said of Hamill. “He’s a lot of fun, he’s hilarious in the episode.”

As for the fate of “The Big Bang Theory” itself, Galecki re-iterated the plan is for the show to wrap after next season, though added no decision has been set in stone.

“It’s not for me to say or predict. That’s the plan right now,” he said. “We’re operating under what we know at this point, and the only discussions that we’ve had amongst the cast is that we’re going to be very sad when that day comes.”

Watch the video above for more.