SPOILER ALERT: Do not read if you have not watched “The Proposal Proposal,” the Sept. 25 11th season premiere of “The Big Bang Theory.”

It was a no-brainer that the 11th season premiere of “The Big Bang Theory” had to open seconds after Sheldon (Jim Parsons) got down on one knee to propose to Amy (Mayim Bialik). But what wasn’t initially as clear, says executive producer Steve Holland, was whether she would immediately say yes.

“As we were breaking that episode, we talked about if there was a possibility where he tells her about the kiss and that makes her hold off on saying yes,” Holland tells Variety.

But what ultimately swayed him and his writing staff, though, was the fact that Amy is “so in love with Sheldon” and “this is the thing that she has wanted for so long,” he says. So Holland felt like delaying the inevitable “yes” would feel forced for the character — and cruel to the audience.

While Amy answered positively within the cold open of the episode, though, there was still a minor delay, as Sheldon felt he had to get permission from someone very special first: Stephen Hawking. Sheldon’s science idol has been on the show before, and Holland says that when they were discussing who Sheldon would call with such a big decision, no other names came up but Hawking’s. “He’s been such a friend to the show over the years,” says Holland. “He’s always been so generous and said yes to anything we’ve asked him to do, and this seemed like a great way to bring him back.”

Holland promises that wedding planning is going to be a “big part” of the 11th season, though he admits it hasn’t yet been decided if Sheldon and Amy will actually walk down the aisle before year’s end. “We’re not that deep into the season yet, so we don’t actually have plans for the finale yet. It’s certainly a possibility,” he says.

Another major part of the season will be planning for a new baby for Bernadette (Melissa Rauch) and Howard (Simon Helberg), who learned they were pregnant again in the premiere. “One of my favorite scenes in the premiere is when she tells Howard the news and his reaction,” Holland says, explaining that Rauch’s real-life pregnancy inspired the on-screen story. “It was so unexpected for the audience but also for the characters.”

Having to juggle a second pregnancy with a new baby is going to “throw them for a loop in a very funny and very real way,” he adds.

Although being parents impacts who Howard and Bernadette are as characters now, Holland is cognizant of not wanting to change the feeling of the show. “Halley’s going to start walking and talking soon, but he’s off-camera as a nod to Mrs. Holowitz and Carol Ann [Susi], who was such an important part of this show,” Holland says.

With so many big milestone changes for so many of their friends, Leonard (Johnny Galecki) and Penny (Kaley Cuoco) are going to start looking at where they are in their relationship and questioning their next steps, too. Says Holland: “They’re together, and they’ve been together for a long time, so a lot of discussion for them this season is, ‘What does that mean?’ They’re happy and comfortable, but everyone else is starting to make these big moves forward, and they’re going to wonder if they should be moving forward, too.”

“The Big Bang Theory” season 11 airs on CBS Mondays at 8 p.m. until Nov. 2, when it moves to Thursdays at 8 p.m.