Wedding bells are ringing on the season premiere of The Big Bang Theory when Penny (Kaley Cuoco-Sweeting) and Leonard (Johnny Galecki) finally tie the knot in Las Vegas.

Despite her concerns about Leonard kissing another woman, Mandy, on his North Sea expedition two years ago, Penny goes through with the nuptials — delivering adorable vows to boot — and the issue of Mandy doesn't come up until their wedding night.

"Penny thinks she may be able to get past it, but it's bothering her more than she expected," executive producer Steve Molaro tells us. "We fly right into the face of it." Unfortunately, they don't fly out of it before the night is over. "They don't end up where they thought they would be and ... it's one of the issues we are tackling in the first couple of episodes."

The Big Bang Theory returns Monday at 8/7c on CBS.

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