Writers Lowell Ganz and Babaloo Mandel have come aboard to do a quick rewrite of Us & Them, the Andy Fickman-directed film. The scribes worked with the film’s star/producer, Billy Crystal, on City Slickers, Forget Paris and Father’s Day.  Us & Them, picked up in turnaround from Paramount, is on a fast track as a co-production between Walden Media and Fox. Crystal plays a grandpa left alone to care for his grandchildren. He has to navigate to overcome generational shifts to bond with the kids, and try to repair a rift with his daughter. They’re rewriting the draft by Lisa Addario and Joe Syracuse.