'The Big Bang Theory': Are Penny and Leonard Back Together? (Video)

The Big Bang Theory Kaley Cuoco Johnny Galecki - H 2011

The Big Bang Theory Kaley Cuoco Johnny Galecki - H 2011

What happens on the 100th episode of CBS' The Big Bang Theory?

Judging from a new promo for Thursday's milestone episode, it looks like the on-again/off-again couple will reunite -- however briefly -- long enough to share one whopper of a kiss.

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On "The Recombination Hypothesis," which co-creator/EP Chuck Lorre describes as being "a little risky, Leonard asks Penny out on a date that appears have mixed results for the loveable nerd. But is it real?

Co-creator/EP Bill Prady told The Hollywood Reporter that the episode will explore Leonard and Penny's past, present and future. “We went back and watched the pilot, and we talked about that, and we tried to do a 100th episode that connects emotionally to the pilot,” Pradysaid at a December event celebrating the milestone at the California Science Center in Los Angeles.

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Co-star Kaley Cuoco told THR that the "100th episode is a real departure for us creatively. It’s definitely a different episode than we’ve done. It’s kind of a brain-teaser a bit; you don’t know what’s going on until then end. The end comes, and then you realize it all makes sense."

What do you think, is the kiss real? Is it a dream?

The 100th episode of The Big Bang Theory airs Thursday at 8 p.m. Watch the promo below.

Email: Lesley.Goldberg@thr.com; Twitter: @Snoodit