Exposed: William and Kate -- Royal Subjects Fooled By Princess Doppelganger (PHOTOS)

Prince William and Kate Middleton caused a huge stir in London by taking their new baby out for a stroll amongst the commoners -- or at least they would have ... but instead a couple of look-alikes did it.

The imposters are definitely dead ringers for Wills and Kate -- and, of course, the baby stroller made everyone think they were getting a first look at Princess Charlotte Elizabeth Diana. Several people shamelessly came up and asked for pictures.

Alas, the fake royals are really just Heidi Agan and Simon Watkinson -- they're kinda famous over there for posing as the royal couple -- but obviously not so famous they can't still fool the kingdom.