I just wanted to jot this idea down and perhaps get some input.
A modern day university. You and your band of friends (3-5 players) are members of an official University Club that everybody assumes is a joke or a way to get University funding and a free room; the Kook Club, or the Kooks. Basically, as the University's Club guide outlines, you collect information on anything weird, strange, or odd in town, and deal with the problem in whatever way you can. While most assume that you're a bunch of cranks, people in the... weirder side of town know exactly what you are. You're the problem solvers - you've all dealt with aliens, vampires, werewolves, wizards, intruding spirits and so on. (It's kind of like the SOS-dan combined with the Scoobies, I guess). And this is another adventure for you...
It's been getting slowly hotter over the past month. Everybody's noticed it; the weathermen spout lines from the Bureau of Meteorology, attributing it to an unusual front from the south; conspiracy theorists post about the secret super-heating weapon the government is testing over town, and electronics stores tell anybody who can listen that air conditioners will combat this hot weather, yes-sir-ee! They're all wrong.
The weather is still getting hotter, and hotter, and hotter, and slowly but surely, it's wearing away at people's inhibitions. People are finding it more difficult to control their impulses, just the little ones at first (buy an extra packet of chips. Take somebody's pen) to the more moderate ones (ask somebody out. Act like a jerk to someone you secretly dislike) to the major ones (take some clothes off to deal with this heat...).
Also, anybody old enough to have an obsession with sex, is beginning to think of sex more and more and more...
(for the purposes of this game everybody under the age of 16 is automatically not old enough to have an obsession with sex; somewhat unrealistic, but it won't get me banned. :3)
Your group of friends start out split up all over campus and around the nearby shopping arcade when everybody around you starts to suffer a critical impulse control failure (that is to say, they will start acting incredibly impulsive) and, well, lusty. Players will begin to suffer from a reduced impulse control (they're not going to start actively trying to have sex with people, but they're going to find it a little difficult to control themselves and their thoughts) but not suffer from the lust at all. Your goal for the moment is to get to the clubroom and try and figure out what is going on (and this is your goal because you all recognize this as one of those 'weird' kind of situations, and you have to get to your library to figure out what's going on).