'The Big Bang Theory' Season 8 Spoilers: Who is Bullying Leonard and Sheldon?

Secrets come tumbling out in the next episode of "The Big Bang Theory" when the girls get together and discuss their past.

Penny's gorilla movie, Bernadette's beauty pageant days, and a fan-fiction story written by Amy involving her and Sheldon is going to cause some serious embarrassment to the girls in the episode titled "The Troll Manifestation."

But the highlight of the episode is Sheldon and Leonard being trolled by someone who doesn't think their widely accepted paper is all that great. Leonard initially tells Sheldon to ignore the troll named "GeneralRelativity", but they decide to find out who it is when the person posts even more harsh comments. The troll is soon revealed to be Professor Stephen Hawking, who admits to posting harsh comments just for the fun of it.

In the meantime, Amy's story involving her and Sheldon will get Bernadette and Penny hooked. The story describes a guy named Cooper who travels back in time and meets a pioneer woman named Amelia. They gradually fall in love and he Cooper refuses to go back saying there is no future without Amelia.

Synopsis of "The Troll Manifestation" reads: "Sheldon and Leonard publish a paper based upon an idea by Leonard which is widely accepted except for comments by one Internet troll. The girls start perusing embarrassing things from their pasts, like Penny's gorilla movie, Bernadette's beauty pageant days, and a fan-fiction story written by Amy involving her and Sheldon."

In other "The Big Bang Theory" news, "Castle" actor Nathan Fillion is set to cameo as himself in the 19 February episode.

The episode will have Raj and Leonard see Fillion, who has starred in "Firefly," sitting at a restaurant and they debate whether it is him and if they should ask him for a picture.

"The Big Bang Theory" airs Thursdays at 8 p.m. ET on CBS.