Kate Middleton visited the set of 'Downton Abbey' and everyone freaked out

Must be nice being a princess -- a couple phone calls and you can just hang out on the London set of your favorite TV show. At least, that's how we're assuming Catherine, Duchess of Cambridge (a.k.a. Kate Middleton) landed a visit to "Downton Abbey," the British drama that's such a worldwide phenomenon even she and husband Prince William tune in.