• ''The Big Bang Theory'' stars Kaley Cuoco-Sweeting,  Jim Parsons, Johnny Galecki, Simon Helberg, Kunal Nayyar, Melissa Rauch  and Mayim Bialik.

''The Big Bang Theory'' stars Kaley Cuoco-Sweeting, Jim Parsons, Johnny Galecki, Simon Helberg, Kunal Nayyar, Melissa Rauch and Mayim Bialik. (Photo : Reuters/Mario Anzuoni)

It appears that a couple is set to break up in "The Big Bang Theory" season 9. Will it be Leonard (John Galecki) and Penny (Kaley Cuoco-Sweeting), Sheldon (Jim Parsons) and Amy (Mayim Bialik), or Raj (Kunal Nayyar) and Emily (Laura Spencer)?

"The Big Bang Theory" season 8 ended on May 7 with several cliff-hangers. It featured Leonard and Penny reassessing their relationship after Sheldon points out that they have set a wedding date although they have been engaged for a year already.

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In response to Sheldon's reminder, Penny and Leonard decide to go to Las Vegas. A confession from Leonard during the trip, however, almost ruins their spontaneous plan to get married in Las Vegas.

It is not Leonard's confession that makes Penny mad; it is the timing. The confession is Leonard once got drunk and kissed another woman years ago. They were still dating but not yet engaged at the time.

For Penny, Leonard is trying to sabotage their Las Vegas wedding but Leonard assures her that he is wholly committed to the wedding so they eventually agree to go through with it. It is yet to be known, however, if a twist in "The Big Bang Theory" season 9 will shocks fans with an aborted Las Vegas wedding plan and a breakup.

In "The Big Bang Theory" season 8 episode 24 titled "The Commitment Determination," Sheldon and Amy's relationship is also not in a smooth ride. The two clearly love each other but Sheldon has no idea how unhappy Amy feels about how slow their relationship is moving.

Like Amy, Raj is not happy with his relationship with Emily as he finds his girlfriend too weird for him. He then plans to break up with Emily while they are in a graveyard but things turn upside down. He tells her that he loves her and is not able to even tell her how unhappy he is about the relationship.

It is highly unlikely that "The Big Bang Theory" season 9 will shock fans by killing off a main character just as how "Grey's Anatomy" season 11 killed off Patrick Dempsey's character Dr. Derek Shepherd.

On the other hand, a likely twist in "The Big Bang Theory" season 9 can be a breakup between any of the three pairs of lovebirds Leonard  and Penny, Sheldon and Amy, or Raj and Emily.