'The Big Bang Theory' Season 8 Spoilers: Sheldon Becomes Ultimate Fanboy With 'Firefly' Star Nathan Fillion?

"Castle" star Nathan Fillion will make a cameo in an episode of "The Big Bang Theory" season 8, according to the spoilers from Entertainment Weekly.

The report said that Nathan Fillion will appear as himself as Sheldon and the rest of the gang will go all nerdy when they get the chance to meet the "Firefly" actor.

According to "The Big Bang Theory" season 8 spoilers, Leonard (Johnny Galecki) and Raj (Kunal Nayyar) will spot Nathan Fillion sitting by his lonesome inside a restaurant. They argue whether or not it's really the actor, and whether they should head over to ask for a picture.

The website also published a photo showing Raj and Leonard grinning as they poses for a selfie with the less-than-amused Nathan Fillion.

"The casting comes as no surprise, considering how much 'Firefly' has played a role on the series," the article noted. "Sheldon (Jim Parsons) is a huge fan of the show and frequently laments its premature cancellation-he initially included a clause in the roommate agreement dedicating Friday nights to watching the sci-fi series since he believed it would last for years to come."

Prior to Nathan Fillion's cameo on "The Big Bang Theory" season 8, Sheldon and Leonard will have to contend with cyber bullying.

The synopsis for "The Troll Manifestation" reads: "After Leonard and Sheldon co-publish a physics paper, they must defend themselves against criticism from an online bully. Also, girls' night finds Penny, Amy and Bernadette confronting embarrassing moments from their past."

This particular episode was written by Steven Molaro, Eric Kaplan and Tara Hernandez and directed by Mark Cendrowski. The guest stars include Jim Meskimen as the doctor and voice over.

Watch out for more "The Big Bang Theory" season 8 spoilers which will be published here ahead of the airing date on Feb. 19.