Ooooh yeah, there's been a few times when the full bladder light was glowing red!!
Only really happened on the Coastwatch flights if I drank my can of Coke too early in the flight. (ave sortie lengths 4-6 hours, Islander, no toilet). A quick divert to the nearest aerodrome would be the order of the day. (there's a funny story with one of those diverts too)
A colleague has had a pax with the runs. Pointed and squirted into a sick bag in front of the other punters. (scenic flight in a Partenavia). Didn't spill a drop. (note, sick bag we used were foil lined chicken bags)
Always went to the loo prior to flight. Still do. A 30 min flight can so easily turn into a 2 hour number!!