The young royal was snapped sticking her tongue out for the cameras during a charity event on Thursday (08.08.19), drawing laughs from a crowd of onlookers.
Charlotte was with her mum, the Duchess of Cambridge, at a regatta event in Cowes, Isle of Wight.
Kate was bending down next to Charlotte and pointing to the photographers, smiling as she tried to get the child to wave.
But the youngster put her tongue out instead, causing the crowd to laugh.
Kate, grinning, lightly chastised Charlotte and moved her on.
Mum-of-three Kate, who also had six-year-old Prince George with her, was there with William to raise cash for their charities.
Their youngest, 15-month-old Louis, was not at the event.
It's not the first time Charlotte has delighted photographers with her sassy personality.
According to Express, last year she insisted one poor pap wasn't invited to Prince Louis' christening at St George's Chapel, telling the man: "You're not coming!"
Charlotte turned four in May and reportedly celebrated the milestone with a suitably "rowdy" party with her pals.
William is understood to have told children's author Julia Donaldson about the family's party plans.
Julia met William when she received a CBE and he spoke about Charlotte's birthday celebrations.
Speaking to ITV News after meeting the royal, the writer revealed: "He said it's his daughter's birthday today and he loves the book.
"He reads my stories to his children, and he said he was going to have quite a rowdy party - he's got a lot of children [coming]."
On her birthday, the Cambridges shared cute snaps of Charlotte on social media.
Three official photos of the little girl were shared to the Palace's Twitter page, showing her smiling for the camera as she played outside.
And royal fans couldn't believe the resemblance between Charlotte and her great grandmother, the Queen.
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