What to do at my party?!

There are many ideas. Just about everyone loves pizza, if someone can't eat or prefers not to eat chocolate. You need a second alternative for food.
As far as activities, karaoke is a great idea but have another activity planned should this one bomb.You can get used T-shirts at a thift store for almost nothing. With a couple of magic markers or permanent ink pens, have them write messages on the shirts.
You can also have everyone bring gag gifts (say under three dollars) and draw names or numbers (each person has a number). This should be a real hoot. Then at the end, they could trade their gifts or use a system where the top number gets the top pick, second number gets second pick of the gag gifts and so forth.
I presume alcohol is illegal and can be dangerous for teenagers!
As far as drinks, you could have frozen kool-aid in ice trays and put sticks in them for handling. I hope that helps.
You could also play the Story Game. It's a little complicated but . You hand an 8-1/2" x 11" piece of paper to everybody with pens or pencils.. You have everyone sit in a circle. You make up a group story. This is how it works. In succession you name a girl present and pass the paper,then name a boy presentand pass the paper, then name where the boy meets her, then what she said, what he said, what she did, what he did, passing the paper each time and folding the answer down to make a composite story. Then have them say what the world said, what the moral story is...you can add your own questions but keep it to ten or less and make the paper folds not too large otherwise the paper runs out. At the end have the person read their composite story going around in the circle. It's a hoot. I hope that helps!

I'm a researcher.

I would set up a stage for Karaoke . Have ppl sing to you . Also its almost halloween so get a fog machine and strobe lights. Another idea would to get flash lights from your dollar store and then replace the lenses with colors. Have your guest turn them on and off during songs.

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find black lights and replace the bulbs in that room with black light bulbs, then have posterboard and markers that will glow and people can draw signs. maybe have blank t shirts and people can write on each other?

Video games (Rock band, Guitar hero, Wii, PS3, Xbox)!!!
Karaoke :)
Twister and other board games
Spin the bottle?
SILLY STRING

If there is going to be black lights give everyone a white t-shirt to wear and have a bunch of highlighters so you can write all over each other.

well my party i had chocolate fountains but get a jukebox thats really entertaining singinig kareoke is fun and people would have a good laugh but get a fairy floss machine all me and my frineds went on high after it we had an awesome night..

Dump some vodka into that fountain and get wasted..
YEAHHH