Rosie O'Donnell flung her last koosh ball today as the 40-year-old entertainer's six-year talk show career came to an end. "This is the biggest, gayest celebration since Liza's wedding," cracked guest Nathan Lane. Also stopping by to say farewell: O'Donnell's pal Christine Ebersole and her No. 1 obsession, Tom Cruise. The Mission: Impossible superstar appeared in a taped segment fulfilling O'Donnell's ultimate fantasy: cutting her lawn.