'The Big Bang Theory' previews Leonard and Penny's wedding

LOS ANGELES, Sept. 18 (UPI) -- The Big Bang Theory released footage of Leonard and Penny's wedding Thursday.

The preview sees the characters, played by Johnny Galecki and Kaley Cuoco, respectively, prepare to walk down the aisle in Las Vegas. The couple decided to marry despite Leonard admitting to kissing another woman, but it has yet to be seen if their nuptials will go off without a hitch.

"The show is moving forward in big, brave ways and so are Leonard and Penny," executive producer Steve Molaro told Entertainment Weekly. "She knows they've been together a long time. She's telling herself ... 'I can get past [the kiss]. Let's keep moving forward.'"

"People have rocky patches in their lives -- Sheldon and Amy and Leonard and Penny," he added. "You can either give up or you can work on them. I would say, for both couples, sometimes things need to get worse before they get better."

Jim Parsons and Mayim Bialik portray Sheldon and Amy, with Simon Helberg as Howard, Kunal Nayyar as Raj, Melissa Rauch as Bernadette and Kevin Sussman as Stuart. The Big Bang Theory premiered in 2007, and will return for a ninth season Sept. 21 on CBS.