‘Big Bang Theory’ Season 9 Spoilers: 6 Things To Know About The New Episodes Before The Sept. 21 Premiere

“The Big Bang Theory” Season 9 is going to have plenty of relationship drama. Spoilers from the CBS comedy reveal a major focus on Penny (Kaley Cuoco-Sweeting) and Leonard’s (Johnny Galecki) relationship and Sheldon (Jim Parsons) and Amy’s (Mayim Bialik) feelings for each other. Check out what “Big Bang Theory” fans should know about the upcoming episodes:

1. Sheldon’s Emotional Boundaries Explored -- Sheldon and Amy will deal with the aftermath of Amy’s decision to take a break from their relationship last year, but their future isn’t set in stone. “Jim Parsons and I are still curious where it’s going to go,” Bialik told TV Line. “[The writers are] really experimenting with what this is bringing up for Sheldon and what it means for him and how far he can be pushed emotionally.”

2. Sheldon’s Proposal Plan -- Audiences will find out more about Sheldon’s plan to ask Amy to marry him. “Big Bang Theory” will reveal how long he was holding onto that engagement ring and his mindset when he was planning to propose.

3. Sheldon Wants Amy’s Forgiveness -- Sheldon wants his relationship with Amy to go back to the way it was, but he won’t go about it in the right way. “His thought processes can get pretty misguided in that that he thinks, ‘Oh, this will make her jealous and make her like me again,’ but that will only make her furious,” Showrunner Steve Molarotold the Hollywood Reporter. “He's not good at leaving her alone. The one thing she asked for was a little bit of time to think and he's not going to give that to her.”

4. Penny and Leonard’s Wedding -- Penny and Leonard will get hitched in the Season 9 premiere. Leonard and Penny’s Vegas wedding isn’t exactly what dreams are made of in a new sneak-peek video. The couple looks more in love than ever, but the ceremony isn’t a fairytale. When the chapel runs out of rose petals, potpourri from the bathroom is offered instead.

5. Leonard’s Mystery Woman -- It might not be all about marital bliss for Penny and Leonard. The show cast Melissa Tang as Mandy, the woman Leonard kissed on a North Sea expedition. Her appearance might ruin Leonard's newlywed bliss.

6. Road Trip -- Season 9 won’t just be about relationships. The gang will hit the road in an upcoming episode without any of the women. “There will be a fun road trip to Mexico for the guys early on,” executive producer Steve Molaro told Entertainment Weekly. “The road trip will be taking place in [the late theoretical physicist] Richard Feynman’s van and it will actually be Richard Feynman’s real-life van that we have access to -- his actual van from the '80s with the equations that he had painted on the outside of it.”

“The Big Bang Theory” Season 9 premieres Monday at 8 p.m. EDT on CBS.