George Clooney joined his Gravity costar Sandra Bullock and her adorable little guy, Louis, on the set of the film in London yesterday. The actor used his iPhone to capture some pictures of the supercute tot, who looked precious in a wide-brimmed hat, and chatted with Sandra. George might not have any kids of his own, but he does play a dad in the upcoming The Descendants, and he seemed to have an easy time tapping into his paternal side around Louis. Sandra is back to work after taking some time off during her son's infancy. She just started working with George on the drama about a space-shuttle disaster and recently wrapped filming Extremely Loud and Incredibly Close opposite Tom Hanks. Louis has been a frequent fixture behind the scenes on her movies this year, and it's no surprise that the Oscar-winning mother is among your favorite celebrity moms in the 2011 Pop 100.