I had been at a meeting in Oslo for the day. I took an early flight from Bergen, where they served us breakfast. I had not drunk my carton of orange juice when they came to collect the trays, so I put it in my pocket for later.
After the meeting, I was back at Gardermoen Airport, standing in the security queue. Right behind me there was a young man in snow-white jeans. They seemed to be new, and occasionally he rubbed off a speck of dirt or dust. He was clearly quite proud of them.
Then I remembered the orange juice. I was loath to throw it away, so I decided to drink it there and then. Unfortunately, I must have squeezed the carton too hard when I pushed in the little drinking straw. A fine jet of orange juice sped away behind me and landed on the white jeans.
The point of impact could hardly have been more unfortunate. The colour and location of the stain made it reasonable to assume that urine was the cause.
If one had planned to do this on purpose in a sketch, it would probably have taken many attempts.