Once in 1998 I booked on a domestic flight from Caracas to Santa Elena. There were only about 10 other PAX so the airline chaged from a 737 to a smal jet with no toilet. The proposed 2 hour flight was going to be 4 hours as a result.

It was an early morning flight and I'd had a large juice and coffee. To cut a long story short, half way through the flight the pilot did an emergency landing at Cuidad Bolivar so I could us the toilet.

Highly embarrassing!!

(In fact I told this story to a few friends back in the UK, and they just refused to believe it, so I normally don't tell anybody about this incident anymore)