I just noticed the white fur/skin around the rabbit's mouth doesn't go all the way round to the back of its head in the boss cut scenes like @ 3:20 but in the ending it does @ 14:38.
I thought the game overall was great but that final boss was awful. I didn't bother beating it in the end, just straight to RU-vid to see the ending lol. I did everything else 100% up until that point.