This is me whenever I watch the same movie I did monthes after watching it the first time, which it wasn't scary to me the first time, but monthes later I freak out at the tiny stuff. Like Cloverfield, the first time didn't scare me at any part, but way later I freaked out at any sound off-screen.
I mean, like the old Alien movie, with the Xenomorphs and the facehuggers? First time watching it *granted it was 'old' effects* I actually thought of jokes to say at every part that was supposed to be scary. Like the 'Gimme a hug' moment.