Johnny Galecki, Kaley Cuoco Johnny Galecki, Kaley Cuoco

To mark its 100th episode, The Big Bang Theory is trying a first — and it has Kaley Cuoco slightly nervous.

"The episode is a little different from what we've done. It plays a misguided trick on the audience until the end, so people might be confused, but it's very well done," she tells "I hope people like it! The audience that we shot in front of loved it, so that's a good start."

Check out photos from The Big Bang Theory

Titled "The Recombination Hypothesis," the milestone episode centers on the relationship that started the hit series: Leonard (

Johnny Galecki) and Penny (Cuoco). While calling back to the pilot — when Leonard first laid eyes on Penny, of course — the installment will explore a possible reconciliation between the two after he asks her out to dinner. The promo, as seen below, shows the former couple, who broke up in Season 3 when Penny didn't return his "I love you," locking lips — but that may or may not be real.

"It's one of those what-ifs," Cuoco says. "We see what they're both thinking a little bit and what everyone's feeling. They're both kinda like, 'If we do go on this date, what will happen?' They both build it up in their minds and then you find out in the end what's really going on, but there are definitely a lot of questions throughout. It was extremely smart and well-written and witty. It's a slightly different angle, and after five and a half seasons, you have to take some chances."

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Because of the various scenarios floating around in their heads, nothing really happens in the episode until the end reveal, Cuoco says. That will set up the following episode, which will offer more insight into whether Penny and Leonard get back together. "They're not done," Cuoco teases. "The dinner is going to be a good jumping-off point to what they're going to start and try doing."With Penny having drunkenly admitted to Raj (Kunal Nayyar) that she regretted breaking up with Leonard, would it be fair to assume that she wants to start dating again? "I think even if she wants to, there are a lot of things to [consider] and it's definitely not easy for them to just start dating again," Cuoco says. "Their friendship is finally going well. I think what people can expect is that they're a little older now, slightly more mature, so there won't be some crazy, horrible drama. They each understand where the other stands."Still, Cuoco — who does not know the writers' plans for Leonard and Penny — believes that it will "take awhile" for the duo to work everything out and truly reunite. And when they do, she hopes it's for good.

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"I do hope they end up together. I don't see the show ending any time soon, so it would probably be awhile down the road," she says. "I enjoy the back and forth. It's extremely realistic, especially when two people live next door and have dated and have loved each other. You break up and you have to deal with your friends and think, 'I don't know. I may still love this person.' Leonard is very special to Penny and vice versa. I think they foresee that this could be a life-changing relationship, but I think that's also why they're moving slowly with it and are looking back and ahead."As far as looking back goes for Cuoco, that's one thing she doesn't want to do — when it comes to the pilot at least. Executive producers Chuck Lorre, Bill Prady and Steve Molaro re-watched the pilot before writing the 100th episode, but Cuoco made sure to steer clear of it."Oh, no. I've seen that thing way too many times!" she says. "It's a great pilot — I'm so proud of it and I love that [this episode] takes us back to it— but I can remember every outfit I wore in that. I don't need to see that again for a while! Maybe by the 200th!"The Big Bang Theory airs Thursdays at 8/7c on CBS. Watch a clip from the 100th episode below.