Here's the story of Schlitzie the Pinhead, a circus sideshow performer who was born with microcephalus and Down Syndrome:
For much of his career, Schlitzie was billed as female. This was mostly due to his dress-like attire which was an attire choice based purely on his incontinence. While popular with crowds, Schlitzie’s biggest fans were his colleagues and caretakers. To sum up the reason for this fondness is difficult but the wonderment Schlitzie held for the daily mundane, his childlike exuberance, his eternal innocence greatly influenced those around him. Schlitzie was a ray of sunshine, and his smile and unconditional love shined on all those around him.
If he looked familiar, that's because Schlitzie was part of the inspiration for Bill Griffith's Zippy the Pinhead [wiki] (the other part was Zip the Pinhead [wiki]).
Link (with video)