I had such a moment today, and wondered if others had similar to share.
I hopped on a train with my MTB in order to spend some time at a nature reserve, as I am off work and it is actually sunny (and bloody cold). Across from me were a yoof and his girly. She was in the usual skin-tight jeans, with approximately seven feet of false lashes weighing down each eyelid. He was probably about 5'7", with a bluebird tattoo on the back of his right hand, but appeared to weigh around the same as the plucked chicken he rather resembled. They were sitting with their feet up on the seats, becoz kool.
I caught the eye of Yoof Boy, saying calmly, "Not really polite to put your feet there", and he gave me his best hard bastard stare, which I simply smiled at, before shrugging and giving me the finger.
Fast forward five minutes, and the guard appears. My ticket is fine, along with my Senior railcard. Yoofy Boy has a Kiddy Railcard, which he has used to buy both tickets. Ms Eyelash does not have any card.
Return part of her ticket cancelled; £20 penalty fare issued. Yoofy Boy could see me smiling all the way through the process, and I kept that smile for hours afterwards.