Statistically unlikely combinations of instruments
Ok, this is excluding fiddle festivals etc, but which combos have you been surprised to find in a session? Normally it’s rakes of fiddles but in my home town we had absurd numbers of flutes. Once counted eight flutes out of twelve players on a small stage in a session. Also saw two harpists turn up at an ordinary sesh. "Them flutes are like buses; you wait ages the eight turn up at once"