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'Castle' Castmate Quiz: Nathan Vs. Stana

Description:After four seasons of side-by-side crime fighting, it's clear that Castle and Beckett have come to know one another like the back of their hand, but how well does their knowledge stand up in real life? MORE: 'Castle' Star Heads To The Big Screen Brooke Anderson of The Insider stopped by the set to test Nathan Fillion and Stana Katic on their co-star know how, and you might be surprised how two stand up in our Q&A. (2:31)

Source: TheInsider.com

Tags: nathan fillion , stana katic , the insider , theinsider