Nathan Fillion talks about getting pranked by Jon Huertas on set of 'Castle'

He's best known for solving intricate crimes on ABC's Castle. But the lovable Nathan Fillion can't figure out how to stop getting pranked by co-star Jon Huertas.

Fillion spoke with ABC's Albert Lawrence about the rambunctious pranks that Huertas throws his way on the set of Castle.

"I can always rely on him to put a smile on my face when I'm not supposed to be smiling," Fillion said. "He'll say something or do something and look at you like 'try not to laugh, go ahead, deal with that.'"

Fillion also talked about how he keeps in touch with fans on social media.

"Here's what I've learned: When you have access to something like the internet and you have a voice, anybody can tweet about anything," Fillion said. "There are people on my Twitter feed that I recognize and I go 'oh, that persons always good.'"

Watch the season premiere of Castle Monday, September 21 at 10 p.m. ET | 9 p.m. CT on ABC.

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