Dracula's Control Freak tendencies make sense when you consider the fact that one of the traits of a classical vampire is OCD (specifically, one of the ways to deter a vampire was to scatter rice/poppy seeds, and the vampire would be compelled to count them before it could move on).
Dracula singing "Grow Old with Me" seems like a strange Adam Sandler Shout-Out , but it makes sense when one realizes that he is accepting Johnny despite the fact that his is human, and will eventually grow old.
Quasimodo was supposed to represent people who are considered monsters and are never given a chance because of their looks and is not really a monster at heart, but in that film where all stereotypically "evil" and scary monsters are nice and decent folks, who would do for a more ironic personality flip along with the others than Quasimodo himself?
The guests at the hotel hate humans and freak out just over the appearance of one (even one they've been partying with for the whole night.) The movie never brings up or explains the fact that The Invisible Man and the Hunchback of Notre Dame are also humans in their respective stories. But on the other hand, the Invisible Man and the Hunchback would both have to be fantastically old by 2012, and yet they're still perfectly alive and limber. They must not be human anymore.
Also they hate humans because of how they treat monsters not because of bigotry against them so Quasimoto and the Invisible Man probably were accepted due to not treating monsters badly and being in the same boat as monsters as they were rejected by humans just as the other monsters did.
Why do contact lenses block Drac's hypnotism but windshields don't? Probably because contact lenses are corrective lenses, they refract and change light to correct poor vision. The hypnosis probably uses light to work so it gets messed up by the contacts. Glasses might have a similar issue.
Why are Drac's friends basically bullying the Zombie composers? Because they used to be human, and are weary around them.
Griffin, the Invisible Man, wears glasses. In H. G. Wells' book, it is mentioned that Griffin's pupils are the only part of him that still have some pigment (not enough for them to be visible under ordinary circumstances, though), which is why he's still able to see. However, critics have long pointed out that, even with the pupils intact, an invisible eye would still result in severely blurred images. So, it's only logical that the Invisible Man would need glasses.
It's a common vampire trope (particularly with the genders reversed) but it still bears mentioning that Mavis is 118 years old. Johnny is presumably around 20-something. Even though Mavis looks and acts like a normal human teenager, some can still find it squicky for him to be dating someone who is old enough to be his great-great grandmother.
It also works in the opposite take. If it took 118 years for Mavis to be comparable to a human 18 year old Johnny will be an old man way before Mavis is comparable to a human in her thirties.
Mavis, like all vampires, is immortal, and Johnny is just an ordinary human. Johnny will have to see his eternally youthful wife outlive him, while Mavis will have to watch her husband grow older and older until he dies, something that she's most likely never experienced first-hand since all of her monster acquaintances seem to be immortals themselves (e.g. the patchwork corpse Frank, the mummy, etc).
One related to the game on the Nintendo 3DS: Why the hell are the hotel staff and monsters attacking Mavis? Worse yet, this can even happen in plain sight of her own father and friends, and none of them would lift a finger to help you.
Wanda's pregnancy becomes terrifying when you realize the fact she's a werewolf and she isn't adding just one baby to her already enormous pack - she's having a litter. Now is when you understand why Wayne always look so bitter and stressed everytime we see him with his family.
When Drac returned with Johnny at the ending at the Hotel, we see Mavis severely depressed, sit and crying in silence. But she had the window opened with all the sunlight. She wasn't in her bed, but in a shore of ther room, dangerously close to the sunlight. We see that in this universe that sunlight can hurt vampires and probably kill them after a time. It's quite possible that she intended to end her life...
