A colleague who has serious issues strung our whole team along with takes of his son, who lived with him in his house, which was luckily next door to his parents. The mother had left and returned to Latvia years previously, but was now suddenly starting a custody battle and he was afraid DS would be taken to Latvia and he wouldn't see him.
Of course we were all sympathetic, and gave advice where we could. He left work early several times to pich his DS up from school etc etc.
Then another colleague invited him and his DS to a bbq, to meet her similarly aged kids. He accepted, then the day before arrived at work saying his DF had collected the son from school the day before, and on the way home had hit a tractor and the DS had died.
He was at work 'to give him something to think about'. Turns out another colleague knew his family vaguely, did some digging with mutual friends, no son, no house, still lived with his parents. Complete fantasist.
When he was confronted he was frighteningly angry at being caught out - to the point I was never comfortable working with him again. But others often heard him starting to tell new colleagues all about his son (miraculously alive again) before being called out by someone he'd tricked.
Also a friend in college where we were on a small course - about 15 of us - told everyone she never wore clothes that showed her shoulders because she had scars all over her back from an industrial accident she was in when her mum took her to work in a factory as a toddler. We were very sympathetic. (but appalled by her mum) Then she started having 'gene therapy' to heal the scars. It was successful and she started to wear strappy tops. Then our course covered gene therapy and how it works. In great detail. Her face was a picture as everyone just turned and looked at her. She also told us she was adopted and treated really badly in comparison to her older non adopted sister. Again, thought her family were pretty crap, then saw a pic of her, her sister and her mum, you couldn't tell them apart. Many others, but I can't remember them.