Only known exit from this conundrum is to state "I can't smell anything". You can say this even if you have been arguing for some minutes about who farted, by which time it will have dissipated anyway, and the class can return to DefCon Two.

I actually became good friends with someone a couple of years ago who claimed to have been in the room at the time of the 'incident'. When I met him, he could barely talk due to severe drug abuse over the preceding years (presumably to get rid of the 'nasty' images in his head) and he had a genuine fear of pencils - he was fine with pens but pencils would make him start shaking and crying. In retrospect, he was probably just another guy who took too much acid too young...he's probably dead now.

Maracas were the hand-grenades of the music room arsenal. Best launched from the upper platform in the drama studio, maracas would explode on contact with floor or head, scattering the enemy with small white pellets and imaginary gobbets of flaming napalm.

The corridor cleaning machines with circular furry discs on the underside.
This name must be unique to my school. As a group of us were engaged in some light vandalism of the sixth form common room, the head caretaker walked in and caught us.
Angry, but not having enough respect or guts to challenge us directly, he said "stop that, or I'll go and get Mike Webber". The idea of our Deputy Head, Mr Webber, having an informal first name didn't register, so there was a moment of confusion before someone asked "what's a kwebber?"
The only thing that made sense was that he was offering to tidy up our mess with his massive sandy-wheeled machine. So on we carried.

Our headmaster's wife had the misfortune to commit suicide by hanging herself in the bathroom just around the time that the song Hanging on a Rope by Rocket From The Crypt was in the charts. Being a headmaster, Mr Williams had absolutely no knowledge at all about pop culture, and therefore had no idea why, wherever he went in the school, every kid he encountered was whistling the same tune. Looking back, it's probably just as well he had no idea.

"Smell my cheese", the bully would invite. Cheese famously smelling delicious, you would eagerly bend over to the waiting fist, anxious to see if there is a tiny cube of fragrant cheese concealed within. As you get closer, you become suspicious. There's no cheese here... and then, the bully would punch you in the nose. A pleasing variant of this is when the bully adds "Smell my cheese, would you?" and walks off huffily, as though you've offended him mightily. You are the victim of another imaginary foodstuff. See also "You just drank my wee".

Ste Sammons didn't even bother to make his lies interesting; for instance, a truck once ran over his foot. It didn't break anything, though.
Fucking phew.

A : Guess what? B : What? A : Good guess. Priceless.

Buchan you're a liar. You didn't invent this game because it is a blantant rip off of light-sabre fighting. Everybody knows Star Wars predated Ghost Busters by years you spaz. The game was made all the better by making light sabre noises when the streams clashed.

There was a kid at primary school who claimed that he dreamt that he was eating a giant marshmallow and when he woke up, he had eaten his pillow.

I didn't know that this was a widely-known joke until recently when I was perusing a children's joke book.