Penny and Leonard are finally getting hitched in the promo and stills for The Big Bang Theory season 9 premiere!

The episode, titled “The Matrimonial Momentum,” will pick up where the season 8 finale left off — with Leonard and Penny heading to Las Vegas to make their love official. The preview for the premiere definitely tugs at our heart strings, reminding us of how hard the pair has worked to get to this moment.

But the episode synopsis implies that The Big Bang Theory season 9 premiere won’t be all sunshine and roses for the couple.

“After driving to Vegas to get married, Penny struggles with Leonard’s confession that he kissed another girl,” CBS says. “Also, Sheldon doesn’t know how to act after Amy pushes pause on their relationship.”

The “other girl,” — a scientist named Mandy, whom Leonard kissed on his adventures in the North Sea — will continue to be a challenge for Penny. Mandy will appear in episode 2, played by Melissa Tang.

“[Penny] thinks she’s okay with it, and she may not be,” executive producer Steve Molaro tells The Hollywood Reporter. “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.”

Still, Molaro is confident that at least Penny and Leonard’s impromptu wedding ceremony will give fans the touching moments they’ve been waiting for.

Related: Mayim Bialik teases beginning of The Big Bang Theory season 9

“I think when you see the premiere, you will feel that it’s satisfying,” he says. “There’s a really special moment, despite all of the things that are happening, that I think makes Leonard and Penny — and especially their vows — truly a magical moment that I’m really excited about.”

Meanwhile, back in Pasadena, Laurie Metcalf will reprise her role as Sheldon’s awesome mom, Mary Cooper — presumably to help “Shelly” get over his changed relationship with Amy. Sheldon’s new, uncertain status comes through in the promo photos from “The Matrimonial Momentum,” as the scientist appears to take Amy’s decision badly.

The Hollywood Reporter also shares a few very touching shots from Penny and Leonard’s elopement. These images definitely make us hope that the Mandy thing fades into oblivion like blasted particle — the sooner, the better.

The Big Bang Theory season 9 premiere, “The Matrimonial Momentum,” airs on Monday, Sept. 21 at 8:00 p.m.

What developments are you excited to see in ‘The Big Bang Theory’ season 9 premiere?