'Big Bang Theory' Season 9 Finale Cliffhanger Ending Explained by Showrunner

SPOILER ALERT – Do not continue reading if you don’t want to be spoiled on The Big Bang Theory finale!

The season nine finale for CBS’ smash hit comedy series The Big Bang Theory aired on Thursday night (May 12) and now showrunner Steve Molaro is explaining the cliffhanger ending.

The episode had the introduction of Judd Hirsch as Alfred, the father of Johnny Galecki‘s character Leonard.

“It started a few months back when Johnny and Judd met [at NBC's James Burrows tribute] and started talking and Judd expressed an interest in playing Leonard’s father. We thought he was amazing as Alfred. We started wondering how and why he comes to town and what could be fun about that,” Steve told The Hollywood Reporter about how the new role came about.

Click inside for spoilers on the cliffhanger and an explanation for what happened…

With Penny (Kaley Cuoco) and Leonard’s (Galecki) wedding approaching, Leonard’s father Alfred (Hirsch) comes into town and falls for Sheldon’s (Jim Parsons) mom Mary (Laurie Metcalf).

The episode ends with Mary and Alfred going to their hotel for a nightcap while Leonard and Sheldon squirm over the idea of their parents together.

Here is what showrunner Steve Molaro said about the episode:

On the abrupt ending: “In the vein of cliffhangers, there tends to be an abruptness to it. Everything that we needed to take care of in that episode got taken care of. If it left you feeling like you wanted more, then hopefully we wrote it correctly (laughing).”

On how the new relationship came about: “We know there’s always electricity and energy between Sheldon’s mom and Leonard’s mom. That was the beginning building blocks that led to [the idea that] if there was another little wedding ceremony to take place, that would be a legitimate reason for all the family members to come back and meet. Once that was floating around, this ending of Sheldon’s mom and Leonard’s dad hitting off started to seem really fun to us.”

On what’s in store for season 10: “Right now, it’s to continue with the stories that are in play. We have all these family members that are there and hopefully more to meet for the first time. We can continue with this guidance system and see where that goes professionally, personally and financially. There’s a baby on the way [for Howard and Bernadette], Penny is unhappy with her career. There are a lot of pieces already in play that for now, we just want to continue with.”

On if there’s a time jump for season 10: “The plan for now, and it’s not set in stone, is that we’re coming back right back into the situation that was created the night before [with their nightcap].”