They really have retconned Castle's character now, from someone who pretends to believe in supernatural mumbo-jumbo to mess with Beckett to someone who sincerely believes in everything.
I know you've mentioned this issue several times before, but this is the first time it has annoyed me. In the past, this was the kind of nutty thing Castle would go on about just to get a reaction out of Beckett -- and it was amusing to watch. But the fact he was serious about the Bigfoot stuff was ludicrous. They even had Alexis acknowledge that he believes in all these weird & crazy things, so it's not just our perception of the character that has changed -- it is his character that's changed, and not for the better IMO.