Mary-Kate & Ashley's Birthday Pop Quiz

Which sister was born first? Who's making a TV comeback? As they turn 21, test your knowledge on the world's most famous twins. By Caryn Midler

Q: 1 of 7

Correct Answer: Ashley

Ashley was born two minutes ahead of her fraternal twin on June 13, 1986, but it wasn't long before both girls headed for center stage. At nine months, the sisters beat out nine other sets of twins to be cast as Michelle Tanner on the ABC series Full House, a role they shared for eight seasons. "They were more open to strangers," the show's executive producer Jeff Franklin told the Washington Post on how the Olsens won the part. "They were smiling all the time."