Before they could get to their official duties, inaugurating the studio in Leavesden, about 20 miles outside London, Prince William, 30, poked a little fun at his younger brother.
"Harry's just excited to see a real-life talking owl in the Harry Potter studios," he said of the 28-year-old prince. "I haven't told him yet that Harry Potter is fictional, so please keep the secret for a little longer."
With that, the fun-loving trio was off, giggling and joking while visiting the Great Hall, learning to cast spells on Diagon Alley and getting a wand lesson and an invitation to "duel" with one another in the Gryffindor Common Room.
Getting a glimpse at the royals at ease were 500 children and their parents, all pulled from charities that have one of the royals as their patron, who joined the tour of the studio's "The Making of Harry Potter Attraction," according to the U.K.'s Mirror.
Duchess Kate, 31, displayed her growing baby bump in a polka dot dress from Topshop, which she paired with a cropped black blazer. The mom-to-be also showed no signs of slowing down in black pumps paired with a matching black clutch.
The duchess's traveling partners, William and Harry, were dressed in their usual suits and ties but that did not stop them from jumping right into the action as they also got a behind-the-scenes look at another of the studio's famous movie franchises, "Batman."
Prince William got a big laugh when he sat in the film's "Batpod" and joked to his younger brother, Prince Harry, "We should borrow it for the weekend."
The prince, set to become a first-time dad in July, was so enthralled with the high-speed machines, he also tried out the "Batmobile" that he perhaps envisioned himself and the duchess cruising along the English countryside in as a family of three.
"You don't do baby seats for those cars, do you, by any chance?" he asked his guides, according to a tweet from a royal reporter at the event.
William also, intentionally or not, got a laugh when he suggested he'd be willing to give up his royal life, at least temporarily, for a chance at movie stardom.
"Christian Bale's getting old and tired. … I will stand in if I have to," William reportedly told Warner Bros executives during the tour.