CBS released a new video promo in anticipation of Thursday's all-new episode, "The Comic Book Store Regeneration."

In the teaser, Amy and Penny demand that Sheldon open up his door to let in them in. However, he tells them that he is naked. Eventually, he complies and opens up while his pants are down. Amy seemed to be pleasantly surprised while Penny is visibly annoyed.

In addition, "Firefly" and "Castle" star Nathan Fillion will make a cameo on the upcoming episode as himself, reports EW. The geeky gang will be in utter disbelief when they spot the nerd idol in a restaurant. Meanwhile, Leonard and Raj will debate amongst themselves if it is really him or not, and whether or not they should ask him for a picture.

The episode will also honor late actress Carol Susi, who played the voice role of Howard Wolowitz's nagging mother. The 62-year-old actress died last November.

According to TVLine, Howard will struggle to cope with shocking news concerning his mother. "The (presumably) tragic turn of events coincides with the reopening of Stuart's comic book store -- a shop that, much to Howard's shock and awe, features a new seating area filled with furniture from his mom's home."

TV.com reports that the synopsis reads as follows: "Amid the excitement of Stuart reopening his comic-book store, Howard gets some unsettling news; and after teaching Sheldon how to 'let it go,' Penny doesn't practice what she preaches when she learns something maddening about Amy. Meanwhile, Raj and Leonard run into a restaurant customer who looks a lot like actor Nathan Fillion."

Season 8, Episode 14 of "The Big Bang Theory," "The Comic Book Store Regeneration," will air on Thursday, Feb. 19 on CBS.

Watch a preview below.

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