ALOHA TIME! Rocker CHRIS ROBINSON, angry and humiliated after learning about wife KATE HUDSON’s hush-hush hookup hula with OWEN WILSON in Hawaii, is finally filing for divorce, sources say. Chris told pals he’d TALK ABOUT A SURPRISE END-ING! The usually unflappable JACK NICHOLSON, at LA’s Cedars-Sinai Medical Center to get a salivary gland problem checked out, waited patient-ly in an examining room until two men in medical garb and surgical masks walked in and brusquely informed him they were interns sent to perform his “initial workup.” While one picked up Jack’s chart and studied it, the other snapped on a rubber glove, brandished a tube of lubricant – and told the superstar, “Roll over, please, sir…we’ll be doing a rectal exam.” Turning pale, Jack immediately launched into non-stop protest, questioning the outrageous “overkill” of a radical probe for a problem at his opposite end…and was stunned speechless when the “interns” suddenly erupted in hysterical, howling laughter! Ripping off their masks, jokers MATT DAMON and LEONARDO DICAPRIO – costars of Jack’s new flick, “The Departed” – giggled helplessly as Matt gasped at gob-smacked Jack: “Dude…just the look on your face was worth all the planning!” Bum steer: Matt and Leo prank ‘The Joker’ hoped to work things out with Kate, but was so devastated by her sneaky rendez-swoon with Wilson that he hired BRAD PITT’s divorce lawyer to snip the ties that bind.