Jim Parsons and Mayim Bialik

Who would've thought when The Big Bang Theory began that our favorite nerds would actually all find themselves in relationships?

But as the CBS comedy heads towards its sixth season finale, those relationships will take center stage, as some of the boys take new steps while others hit a road block. To find out which couples might be in trouble, TVGuide.com caught up with the cast of Bang on the PaleyFest red carpet Wednesday. Get the scoop:

TV Scorecard: Renewed or canceled?

Sheldon and Amy's remain awkward:
Even though they've made a little progress this season, Amy (Mayim Bialik) and Sheldon (Jim Parsons) are still hopelessly awkward in their relationship — and that will continue in an upcoming episode. "Amy is trying to un-condition some of Sheldon's compulsive thinking," Bialik says. Hilariously, she's trying to break him of a habit that Parsons himself thinks is actually a good thing. "It is revealed that Sheldon has a problem leaving tasks uncompleted," he says. "If something goes unfinished, that's going to eat at him and keep him up at night. She tries to free him of that."

Wolowitz has daddy issues: In Thursday's episode (8/7c, CBS), Sheldon will unearth a letter from Wolowitz's (Simon Helberg) father, which opens up old wounds for Wolowitz. "It's a very emotional topic for him," Helberg says. "It's something that he's been closed off from. Obviously he hasn't opened the letter since it came when he was 18. There's a lot of pent-up, conflicting feelings that are poetically opened just as the letter is opened." Fortunately, he'll find help from wife Bernadette (Melissa Rauch). "We've seen them bickering a lot this season, but we get to see the other side of married life," Rauch says. "You'll see that love that they have for each other."

Leonard and Penny are growing up: The dynamic duo (Johnny Galecki and Kaley Cuoco) will plan a very adult cocktail party in this week's episode. "There's a whole thing in your early thirties about being grown up. That comes into play a little bit," executive producer Bill Prady says. Showrunner Steve Molaro adds: "I'm ridiculously proud of the episode. I may have watched the final sequence at least eight times just because I love it." But will it be as good as the gang all holding hands in the Season 5 finale? "It's different," Molaro says, noting that it has to do with one of the character's emotional scars that has previously been mentioned in passing.

CBS announces finale dates for NCIS, Good Wife and more

Can Lucy and Raj last?
Raj (Kunal Nayyar) has been attempting the impossible by carrying on a relationship with a woman as socially awkward as himself (Kate Micucci's Lucy). So, it should come as no surprise that there will be bumps in the road. "He reads a blog that she's written and it kind of freaks him out," Nayyar says. Their relationship will also play a big part of the finale, executive producer Chuck Lorre says.

Finale time: Speaking of the finale, this year's season-ender will be a little bit different from last season's, which Wolowitz and Bernadette getting married before he took off into space. "If that was big, this will be small," Prady says. Molaro adds that the episode will be relationship-centric, but Prady promises there will be no more proposals this year. 

The Big Bang Theory airs Thursdays at 8/7c on CBS.