AceShowbiz -

Penny (Kaley Cuoco-Sweeting) and Leonard (Johnny Galecki) tie the knot in a new promo for "The Big Bang Theory" season 9. The newly released video sees the couple in their wedding attire as they prepare to walk down the aisle. She rocks a mini pink dress, while the groom dons a dark suit.

Sheldon (Jim Parsons), Howard (Simon Helberg), Raj (Kunal Nayyar), Bernadette (Melissa Rauch) and Amy (Mayim Bialik) are seemingly watching via satellite. It also offers a glimpse of the newlyweds' awkward wedding night as Leonard tries to carry his new wife from the aisle into their honeymoon suite.

"It's season nine and Leonard has been pursuing her since minute three of the series," showrunner Steve Molaro explains why it's the right time for the couple to finally tie the knot. He explains to The Hollywood Reporter, "Even Penny, with all of her commitment issues, is in a mindset of, 'Are we moving forward with this or not? What are we doing?' And they do."

But that's far from a happy ending as things will get complicated when Penny learns that Leonard kissed another woman, Mandy (Melissa Tang), during his North Sea expedition two years ago. On how this will affect the couple's relationship, Molaro teases, "I think when you're Penny, and you have an image that you've cultivated of a person for eight years now and those two things aren't aligning anymore - that can be a difficult thing to deal with."

Penny and Leonard's marriage will also be a new challenge for Sheldon who has been inseparable from Leonard. "They're trying to all figure it out," Molaro dishes on how the three will handle the situation. "We jokingly alluded to the fact that in some way the three of them are kind of married and I think the three of them will need to figure out how this is going to work."

"The Big Bang Theory" season 9 debuts Monday, September 21 at 8 P.M. on CBS, before it moves to its regular time period on Thursday, November 5 at 8 P.M.