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 really, REALLY wanted to be a ninja turtle when I was like 7 or 8. I didn’t let anyone in on that, but I thought if I wanted it enough I might change into one overnight.
I also folded black t-shirts to make a ninja hood and snuck around at night