The hosts parents are out of town for the weekend

Oh man, listen to this- there's gonna be a crazy party this weekend because Main Character's parents are out of town! Your friend tells you that everyone's going to be there, and he's right, everyone will: Main Character, Main Character's Comedic Relief Friend, Main Character's Love Interest, and a bunch of other people that don't really matter. Depending on what time period your movie is set in, pick one of the following ways to express your excitement: It's gonna be dope!
or It's gonna be off the hook! or It's gonna be swell and this is unrelated but I know Ronald Reagan primarily as an actor!

You just showed up to the party and all of the pieces are in place for an epic night: Pool in the back, keg in the front, speakers everywhere playing that one Diplo song that will not age well. One of your friends, however, is trying to make the huge mistake of "not drinking" because of "a dark past" "with alcohol" "that ruined his life," but that's nothing that asking him to drink more than once won't fix. Get ready for a wild night, because he is undoubtedly a Jekyll & Hyde-style monster that won't stop drinking until he's dick-punching cops and barfing on his niece. This will be the night he talks about in AA for the rest of his life.

Someone started a perfectly synchronized dance contest

Because this is a party, everyone is obviously wall-to-wall dancing the entire time, only stopping to play a sexy drinking game, like Strip Poker or Taint Shuffleboard. There's only one thing cooler than Taint Shuffleboard, though, and that's surprise choreography! You'll see five guys in matching outfits jump up on a makeshift stage and bust out a perfectly timed dance that begs the question ... do they always do this at parties? Is this like, their thing? Everyone else seems to be going along with it, just play it cool for WHAAA-?!!! Is that Main Character's Comedic Relief Friend busting a move onstage with the rest of them??! This truly is a CRAZY party!

Uhoh Someone broke Moms expensive irreplaceable vase

Come on, guys! This was Main Character's one rule! It's okay that you guys wanted to party, but why did you have to do it near his Mom's extremely expensive vase that also has sentimental value because something blah blah blah dead grandfather!? Come on, his parents didn't put it on their unbalanced living room pedestal for it to be treated so carelessly! I swear to God, if you guys break anything else and it causes the party to reach a tipping point where Main Character is forced to realize that he no longer has any control, he is going to halfheartedly attempt to SHUT THIS PARTY DOWN.

That girl youve been talking to all night has a boyfriend And that boyfriends gonna kick your ass

Oh my God, you've met your soulmate at this party. People always told you that you shouldn't meet people at a place like this, but where else are you supposed to meet people -- the bank?? Dave and Buster's?? This is all too good to be WHAAA-!!?? She has a boyfriend? And not just any boyfriend, but the biggest, most belligerent Human Muscle Mountain you've ever seen and he's wondering why you're with HIS girl. You better stutter out something like "It's uh, it's not what it looks like," and run for your g.d. life because he's not afraid to murder you. Look in his eyes. He does not fear death.

A semifamous band shows up

Listen, if you're going to throw a great house party, it's gotta have a band with a song you kinda know. We're talkin' Oingo Boingo in Back to School, we're talkin' The Mighty Mighty Bosstones in Clueless, we're talkin' Lustra lead by Hot Topic Matt Damon in EuroTrip. It doesn't matter how you get them there- just say something vague about "calling in a favor"- but there needs to be at least one Jimmy Eat World-equivalent or you're going to be the laughingstock of your surprisingly well-connected in the music industry high school.