Here are some cringeworthy anecdotes from the popular TIFU (Today I F*cked Up) thread that will make you so happy that these didn't happen to you. Hopefully.
I was on the tube on the way to see some friends in North London. Whilst looking around on the tube to pass the time, I noticed someone a few seats down that looked remarkably similar to an old friend of mine who I hadn't spoken to or seen for a while, although this person was a lot rougher round the edges and about 20kg heavier than my friend is.
As the resemblance was uncanny, I decided to sneak a quick photo of the person to send to my friend. When I got out of the tube and regained service on my phone, I sent them a message with the photo with the caption "this guy looks just like you if you packed on some pounds'.