Woolsey suffered from a rare skeletal disorder called Virchow-Seckel syndrome, which caused her to have a very short stature, a small head, a narrow birdlike face with a beak-like nose, large eyes with an antimongoloid slant, a receding jaw, large ears, and mild mental retardation. In addition, Woolsey was bald, toothless, and either completely blind or very short sighted.
One of Woolsey's early sideshow acts was called "Minnie Ha Ha", a play on her name and her native Minnehaha Falls in Georgia. It involved her dancing around in Red Indian costumes, speaking gibberish to the crowd. She then spent some time performing as "The Blind Girl from Mars."
Woolsey rarely reacted to anything around her and often sat motionless in a chair for hours on end. However, she managed to get into a feathered bird costume and dance on the table during the wedding feast scene of the movie Freaks. Although she had no lines, she still made a great enough impression on audiences that it was she who was remembered as "Koo Koo", instead of her contemporary Elizabeth Green the Stork Woman, who also -- confusingly enough -- shared the same billing.