I had a couple classmates that pretended to be vampires back in elementary and middle school. They’d pretend their Koolaid was blood, complain about the sunlight, and bite their friends a lot. Not enough to draw blood, though. I haven’t kept up with most of them, but one guy is a teacher now. He seems pretty normal.
I knew a girl in college who also believed she was a cat (this was 20 years ago). She would also scratch and hiss at people. Additionally, she would randomly meow in class. They would just sit there “cleaning” themselves as well, licking their hands and arms. She wore a pair of cat ears and a tail. It was immensely weird.
Hope she’s still living her best kitty life.