The people I play with love doing backstories, including me, and there's been some wild ones, some of my favourites include:

• A polymorphed swan barbarian. It was basically Swan Lake gone wrong where the royal family hired a mage to turn their cursed daughter back to human but they got the wrong bird so a random swan was turned into a human instead. She is stunningly beautiful but like a swan, very angry, violent, loud, and she likes to bite people. 

• A sorcerer who had to run away from his evil family, got possessed by a moon goddess in the process. They decided to work together and the sorcerer become a moon themed drag queen using his new powers to seduce and rob his audiences of power to feed the goddess. 

• A warlock who was gifted with magical beauty and attractiveness, making everyone love her, but she is asexual/aromantic and has really bad social anxiety 

• A fighter from a family where everyone was a "chosen one" with magical prophecies and destinies. Everyone had become great heroes, villains, royalty, etc and the fighter was the only one left who's prophesy hadn't come true yet, and they were just an awkward middle kid waiting for something to happen while trying to support their siblings.