Shrodinger's fart
The moments when, feeling the fabric leave your arse cheeks, but it could be either a large fart bubble or a sneaky poo. Unsure if it's fart or shart, it being considered to be simultaneously both fart and shart until your pants are dropped & the remnants observed.
"Oh man, I had way to much Guinness to drink last night. I woke up this morning and had to run to the loo after a Shrodinger's fart"