whoever smelt it dealt it
Well worn fart-blame transferral method, first documented in print in an episode of Johnny Fartpants around 1990.
The established order is;
"Whoever smelt it dealt it"
"Whoever denied it supplied it"
"Whoever made the rhyme committed the crime."
Despite some of the best minds in the world working day and night on the matter, no further possibilities have been found. These failures show the difficulties facing innovators; "Whoever tried to tell made the smell" (inelegant) "Whoever passed the buck gassed the truck" (only effective on trucks) "Whoever went to the trouble to needlessly place the blame, probably is responsible for the fart that started the game" (a little long)
written by Ma*za*, Jo* Blyt*, approved by Log

During a particularly inspired bout of smelt it dealt it with my sister, I was overjoyed to come up with 'The one who told the story did the glory'. Despite my best efforts it never moved into common parlance, and with hindsight I see why.
written by Wi*l Jen*ins, approved by Log

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.
written by Dr*Rin*piec*, approved by Log

We always said "whoever rhymed it, crimed it".
Criming something was considered a perfectly legitimate term. A variant would be to run up to someone, shout "Criminal Activity!" and steal someone's bag of crisps, or something.
written by gr*ff ., approved by Log