Robert Downey, Jr. Dons Skintight Green Onesie -- See How the Stars Celebrated St. Patrick's Day

Everyone's Irish on St. Patrick's Day, including some of Hollywood's biggest stars. On Saturday, celebrities like Robert Downey Jr., Pink, Nick Lachey, Brandi Glanville, and Busy Philipps shared photos of their celebrations. While the day is in honor of the Feast of Saint Patrick, the foremost patron saint of Ireland, it's culturally become a day when people dress in green and kick back a pint of beer (or two). For most stars, though, the day was a family affair. RELATED: Luck of the Irish: See ...