The Great Muppet Caper

Our heroes arrive in London to interview Lady Holiday (Diana Rigg), a high-fashion designer whose priceless diamond necklace has just been stolen. But when Kermit mistakes lovely receptionist/would-be model Miss Piggy for her aristocratic employer, it's love at first sight. Unfortunately, Lady Holiday's scheming brother (Charles Grodin) is also wooing the sultry swine -- so he can frame her for another brazen jewel heist! Now it's up to Kermit and his Muppet pals to clear Piggy's name and catch the real culprits. (official distributor synopsis)