* AdvertisedExtra: KirstenDunst is in way less of the film than the marketing campaign made it out to be.
* DeletedScene: In the extended version of Mary's tape, we learn that [[spoiler:Mierzwiak pressured Mary into having an abortion as well as a memory wipe]].
* FakeAmerican: Kate Winslet, Tom Wilkinson (both British) and Jim Carrey (Canadian).
** [[Film/SpiderMan Mary Jane]] loves [[Film/TheAvengers The Hulk]]? [[spoiler:But she actually loves [[Film/BatmanBegins Carmine Falcone]], yeah, you can get your Brain Bleach now.]]
** [[Film/LordOfTheRings Frodo]] is trying to steal [[Film/BatmanForever Riddler's]] girlfriend with his own words!
** As opposed to their usual roles, Jim Carrey plays TheComicallySerious while Kate Winslet plays the ManicPixieDreamGirl.
** From the supporting roles, ElijahWood plays a shallow douchebag.
** The film's title is a quote from Alexander Pope's "Eloisa to Abelard", a passage from which Mary recites to Howard.
** Mary also quotes Creator/FriedrichNietzsche at one point.
* ThrowItIn: A scene length one. While filming in downtown Manhattan, they heard that there was a circus parade going on outside. Gondry grabbed a portable camera, and got some footage of Carrey and Winslet messing around in the crowd completely anonymous due to it being night time and since the actors were wearing winter gear. The result is one of the happier memories in the movie.
* WordOfGod: [[spoiler: In an alternative script there's an extra ending, where an older Clem goes back to Lacuna to erase Joel again, and an older Mary reveals to her that [[ViciousCycle Clem and Joel have been erasing and re-erasing each other for years, always ending up back together]].]]