“Big Bang Theory” season 9 finale offers its fans a huge cliffhanger on Thursday night (May 12).

The cast of the CBS hit comedy series is set to welcome comedy legend Judd Hirsch, who will play Leonard’s father, Dr Alfred Hofstadter. Alfred arrives in town for the wedding of his son to Penny.

In episode 24, titled “The Convergence Convergence,” Leonard’s mother, Beverly, will come face-to-face with her husband for the first time after they got divorced. An awkward moment is expected as Dr Hofstadter will also meet Sheldon’s mother, Mary Cooper (Laurie Metcalf).

Both Penny and Leonard’s parent will attend their wedding since they were not present the first time the couple tied the knot in Las Vegas.

The Hollywood Reporter noted that the events in the finale episode will set the stage for new dynamics in the show.

In an interview with TV Line, “The Big Bang Theory” showrunner Steve Molaro teased what to expect when the estranged couple sees each other once again. “I don’t think things are going to get as physical [as they did on The Good Wife], but verbally she will slap him a few times,” he said.

Molaro said things are going to be “acerbic and caustic” between the Alfred and Beverly. “As far as what is surprising about that, there might be a bit of an unexpected attraction springing up between Leonard’s father and Sheldon’s mother,” he said.

It was earlier reported that Mary and Alfred will hook up, and  Leonard and Sheldon will be shocked about it. If Sheldon’s mother and Leonard’s father were to marry each other, that will make the two CalTech scientists brothers.

In another interview with THR, Molaro teased that the “The Big Bang Theory” season 9 finale will end with a huge cliffhanger.

“We leave [the season] in typical Big Bang fashion – on a bit of a cliffhanger with Leonard, Penny and Sheldon in the living room making sense of everything that’s going on,” Molaro said.

“The Big Bang Theory” Season 9 finale airs Thursday at 8 p.m. ET on CBS.