These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Iron Man tried to justify the murder of Obadiah Stane by reminding Superman and Batman that if you throw a criminal in jail, he'll just swear revenge on you and break out. This bit of Genre Blindness takes effect in Iron Man 2, when dealing with Whiplash.
The conversation Superman has with Iron Man about killing your villains is even funnier after Man of Steel came along.
Squick: Grendel's mother in Beowulf, um, bubbles from a wrong location.
Suspiciously Similar Song: Any time you hear an iconic theme in this series it won't sound exactly like the original, because of copyright rules.
Uncanny Valley: Purposely done to baby Renessmee in Breaking Dawn Part 2, mocking the use of CGI in the actual movies.
Van Helsing Hate Crimes: The end of the "Zombie Song" video could be seen as it, with Chris and Jill mercilessly and thoughtlessly mowing down the singing zombies. That said, they do want to keep their brains.