Nerds unite; Firefly star Nathan Fillion is slated to guest star in an upcoming episode of CBS's The Big Bang Theory.

'The Big Bang Theory' Star Jim Parsons Almost Cast In Failed Sitcom Before Nabbing Sheldon Cooper Role

Fillion will be playing himself in the Feb. 19 episode of The Big Bang Theory, according to a new report by Entertainment Weekly. He will appear in a scene in which he is sitting down at a restaurant where Raj (Kunal Nayyar) and Leonard (Johnny Galecki) spot him. The pair banters over whether or not this is actually Fillion before going up to him to ask for a picture.

As the report notes, Firefly is actually a recurring gag on the series with Sheldon (Jim Parsons) being such a fanboy of the short-lived Fox series. Fillion played Malcolm Reynolds on the sci-fi/western series.

'The Big Bang Theory' Star Mayim Bialik Talks 'Character Depth' As Reason For Popularity & Success

Other geeky credits for Fillion include Dr. Horrible's Sing-Along Blog and Buffy the Vampire Slayer. He is currently starring on ABC's Castle, which is currently in its seventh season.

The sitcom is slated to air two episodes before Fillion's cameo. In the next episode, which airs Thursday, Feb. 5, Leonard and Sheldon face off against an Internet troll.

"After Leonard and Sheldon co-publish a physics paper, they must defend themselves against criticism from an online bully," a synopsis for the next episode reads. "Also, girls' night finds Penny [Kaley Cuoco-Sweeting], Amy [Mayim Bialik] and Bernadette [Melissa Rauch] confronting embarrassing moments from their past."

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