I completely forgot the finale would be 2 hours so missed the first half.
One thing I think I missed while watching the last season, but maybe noticed finally in the last episode was them revisiting old story elements. I missed the episode about why Michael was important so I looked it up on the Fringe wiki and in doing that learned they found Sam, or his body, an element from season 1 and 2. Don't know how he fits into the whole thing since I'm no longer sure if the first one's and their machine "exist" but thanks to that I noticed the butterfly killing scene. I guess the machine exists since the other version of Olivia and that guy were in the final.