The cardboard box that Keith is writing on changes as he writes Nathan's name. There is a bigger gap to write in at the bottom and the crease/fold is in a different spot in the word refrigerator.
When Hailey is having the flashback of Nathan asking her to marry him, you can hear her say, "Well maybe so", yet her mouth doesn't move. And, when Nathan tells her that he never wants to be normal with her, his mouth isn't moving except when he says "normal".