Hooray! It’s … Donald Duncan’s birthday? Yes, Donald F. Duncan is the owner of Duncan Yo-yos, the premier maker of yo-yos.
Duncan yo-yos were not the first yo-yos, however. The quiz, jou-jou, or bandalore has actually been around for thousands of years. It was in China as early as 1,000-500 B.C. and possibly existed in Greece even before that. Though the yo-yo craze that gripped American in the early 1900s has waned, yo-yos remain a mildly popular pastime. And for a few, it obviously remains something of an obsession:

YoYo Blur Shirt (dark) by YoYoCandy
One Of Those Days by sands53042
beware of yoyo ninja by cannonyo
More About Yo-Yos:
How Yo-Yos Work
Throw Yo-Yo Ma from the Train: poster, print, or card by Perspicuity