'Cheers' Star John Ratzenberger SHOCKED By Danny Devito / Rhea Perlman Split

Danny DeVito and Rhea Perlman's split didn't just come as a surprise to their fans ... it also blindsided their close friends -- including "Cheers" actor John Ratzenberger, who claims he had NO IDEA the famed couple was calling it quits.Ratzenberger…