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The reason I started watching Castle was Nathan Fillion. I loved Firefly and I was fan of a number of other projects he’d been in, like Buffy the Vampire Slayer, Dr. Horrible, Waitress, and others. I also knew Susan Sullivan had a long acting career and that Stana Katic had had a number of small parts in popular TV shows before being cast as Kate Beckett. So I started to wonder if they’d ever worked on the same TV series previous to Castle.
What I found was a number of connections that I had no idea existed. This is not to say that these actors appeared in the same episodes together, but that they had appeared on the same series at different times.
What I found most surprising was that both Seamus Dever and JAG seem to be at the center of the Castle universe. Take a look for yourself.

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The picture isn’t enlarging when I click it. Otherwise, what an awesome chart!
Same, I’d love to see this up close. Can’t find it on TV Buzzer either. *sadface*
IT should be working now
It does, thanks!
Great article! Nathan Fillion was also the reason I started watching Castle simply because I had seen him as Caleb on Buffy and thought he was great. This is my favorite show on TV by far and all these actors are fantastic
I only have one tiny problem with this. Ruben Santiago-Hudson was left out.
Yea! He may be a dead character, but he still is one! Great job though… this chart is amazing!
Wow! This is amazing! I can’t believe it!
But great job in seeing the connections.
I’m seriously impress.
Wow! You are definitively a TV Junkie to notice all these connections, impressive job.
It’s a very good surprise to see Castle beeing related with JAG as I was a fan of the latter.
It could be interesting to know, may be NF auditionned for DJE’s character, as actors they do have some common features…
Anyway love CASTLE !!!
I’m a browncoat too! I started watching Castle because I’m a Nathan Fillion fan, but I discover a great show, with others great performers and great writers.
Your job is really nice! funny!