Once, just last month, LAX-ORD. Apparently, a passenger decided to get up and hit the lav right as we were starting our takeoff roll. As we exited the runway, the pilot came on and explained exactly why this had happened and made a big point of wondering whether or not ATC would let us go back to the front of the line or if we would need to wait an extra 20 minutes by going to the end of the line.

It was a 777, so I never could see the mystery peer, but you gotta figure there was some lynching going on when they returned to their seat.

And, of course, yes, ATC let us go directly back to the front of the line.