Someone from Sheldon's (Jim Parsons) past is making a return on "The Big Bang Theory" season 10 finale airing this Thursday, May 11. Speculation is that Sheldon could be cheating on his long-time girlfriend Amy (Mayim Bialik), who left for Princeton for her summer fellowship in the last episode.

Dr. Ramona Nowitzki (Riki Lindhome), Sheldon's big crush from the second season -- before he even met Amy -- is back on campus. Reports say she's not letting Sheldon get away this time. "The Big Bang Theory" showrunner Steve Molaro told TV Line, Ramona is "looking to take advantage of Sheldon" who won't be keenly aware he's crossing the line.

A very unhappy Amy

Obviously, Amy will be unhappy with Ramona's return, especially when she's temporarily 3,000 miles away. Sheldon and Amy will have fights about his friendship with Ramona, which will cause a strain in their relationship. The people behind "The Big Bang Theory" said the latest development has been part of the plan for Sheldon and Amy's character growth since the start of season 10. "In a subconscious way and from the groundwork of the show in general, it adds a layer of something between them," Jim Parsons told Entertainment Weekly.

Fans expect that the cliffhanger episode will bring mixed feelings. "The Big Bang Theory," however, isn't going anywhere and ending the show this way will make the upcoming season more exciting.

Sheldon and Amy made a big step in the current season when they decided to move in together.

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But with this relationship problem cropping up, will this mean another change to their living arrangement if they cannot patch things up in season 11? Will Raj (Kunal Nayyar) become Sheldon's roommate?

Amy was almost a goner

Before the cast shot "The Big Bang Theory" Season 10 finale, Mayim Bialik was in the midst of contract negotiations with CBS. Producers admitted they didn't have an alternate ending should this fail and Amy would have been a goner. Fortunately, it all worked out for Bialik, as well as co-star Melissa Rauch (Bernadette). Both are on board for seasons 11 and 12, along with the rest of the original cast.

Amy was introduced in the third season as a recurring character. At that time, the producers had not planned on developing a relationship between Sheldon and Amy but the timing worked out well.

Meanwhile, Parsons will also be busy helping out with the spin-off series as well. The actor will be narrating the show, which will delve into his character as a child.