According to a report from Entertainment Weekly, Sheldon Cooper (Jim Parsons) has a very big and very weird secret that is about to be laid out in the open before the end of "The Big Bang Theory" season 9. 

"Very soon Sheldon is going to reveal a weird secret to Amy that he's been hiding for a long time that nobody knows about," explained showrunner and executive producer Steve Molaro. Unfortunately, Molaro did not give any hint of what this secret could possibly be.

According to the report, this secret is not related to the engagement ring that Sheldon was going to use to propose to Amy (Mayim Bialik), which immediately rules out any possibility of him proposing to Amy for marriage or that the whole thing may be a hoax of some sort.

Movie Web reports that there are a few realistic suggestions. One accepted rumor is that Sheldon may finally admit he does suffer from some degree of Asperger's Syndrome, although the likelihood of this turning out true is very low given how often Sheldon states that he has been tested and has been proven to be sane and mentally capable.

There is the rumor that the secret may have something sexual in nature, but the likelihood of this is also low given that Sheldon and Amy already had sexual intercourse and this happened with the bedroom lights on, precluding any chance of his secret being about his sexuality or physical deformity.

According to the report, the secret may be very heavy plot-wise and may be used as a cliffhanger to end season 9. "The Big Bang Theory" is known for its cliffhanger endings, mostly with a primary character leaving for an expedition of some sort, and this secret could force Sheldon to leave the apartment for some time until he is fetched in season 10.

"The Big Bang Theory" season 9 returns with episode 18, airing this March 10.