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.
Designated Villain: Rob the neighbor is seen as a big party pooper who doesn't want the partygoers to have any fun, but he didn't even ask them to shut the party down until nearly midnight, and the reason he wants the party to be wrapped up is because he has a child and wife who can't sleep because of the party. But despite his good reasons, he's still treated as wrong, and ends up getting tazed, stalked, tackled and nearly gets his house set on fire for his troubles.
Ensemble Darkhorse: The midget is probably the most beloved character in the movie, mostly because he punches Costa along with many other people in the nuts after he got locked inside an oven. Sure, he's a Jerkass too, but considering nearly everyone else at the party, he's often seen as the lesser of many evils.
Family-Unfriendly Aesop: Admittedly, an age-appropriate one: When you're either 17 or 18 and in desperate desire to be popular; throwing a party to end all parties, costs be damned, is a sure-fire way to make yourself cool.
Jerk Sue: Costa, the person most responsible for starting the party, gets away completely scot-free bar the 3 paternity tests thanks to having a very expensive lawyer.
Then again, he's got three paternity tests hanging over his head. If they all turn out positive, he's royally screwed.
The Scrappy: Costa is well known as an utterly despicable sociopath of a human being by almost every viewer of this movie.
Unfortunate Implications: Apart from Kirby, most of the girls in the film are treated as objects by the main characters. The film never once calls them out on it, and indeed the ending seems to suggest that the experience was a good thing for them.