"Castle" star and Twitter hero Nathan Fillion is one good-looking man. But he also happens to resemble some other celebrities! But which ones does Fillion himself think he looks like?

Fillion has been sounding off on Twitter over the last day about his lookalikes. It started when a fan sent him a pic of a guy at a bar who could be his doppelganger:

This spurred on his 2.1 million followers to submit other lookalikes, like New England Patriots tight end Rob Gronkowski:

Or evil Ethan from "Lost":

Could Fillion have been separated at birth from Jeremy Renner?

Fillion thinks he looks somewhat like Brendan Fraser:

Apparently, he and "Arrested Development" star Jason Bateman have talked about their resemblance:

"Homeland" and "Revolution" star Tim Guinee looks awfully familiar:

We don't think David Boreanaz looks much like Fillion, but we get why people might mix the two up:

Who do you think looks like Nathan Fillion?