Incident in which you take a dump, and the toilet splashes you back in perineum. This is different from a regular bidet in that it's the toilet water that's splashing you, not a directed tap.
As a rule, this nearly never happens at home, and it frequently happens when you're forced to use a stall with overtly nasty waters or after you've already urinated.
person one: I'm a little worried. I had to use the portajohn at the airshow, and it gave me a spontaneous bidet.
An idiot on a bicycle - someone cycling and phoning at the same time without their hands on the handlebars and going through a red light or two generally causing chaos and neglecting all known traffic laws.
Look at that bidiot over there. I hope he falls of his damnbike and smashes his phone.
When you drop a turd with the precise mass, shape and density at the just perfect speed, that lands in the water at the precise angle to send a large splash of toilet water straight back at your brown eye.
Pete: (from inside the bathroom) Awwwwww goddammit!!!!
Craig: (from outside the bathroom) Everything ok in there?
Pete: No, I just got a chunky bidet!
The combination of liquid and aerosol felt when an automatic toilet mistakenly flushes, post-business but pre-standing-up.
Student 1: (Audibly crying and whimpering in a restroom stall)
Student 2: Hey bro. Are you alright?
Student 1: (Behind stall door) No. I forgot to put toilet paper over the motion sensor on the toilet, and I got a Dirty Bidet... I have 4 more hours of classes! (Crying continues)
Student 2: (Shudders, shakes his head with sympathy, and walks away)
The act of a male using his urine in an upwards stream to clean the undercarriage of another person who is squatting over them.
After a long hot day of walking around the Inner Harbor, Ross discovered his ass crack had become excessively lathered in smelly bum butter. Upon hearing of the situation, ever helpful Jim volunteered to accompany Ross back to the hotel and give him a Baltimore Bidet.
"Ross, I've got a belly full of 'Natty Boh' and have enough pent-up piss to easily flush all the jizz infused dung-discharge from your ass crack!"