But who was his unfortunate victim?
Royal events are made all the more fun when the children misbehave.
From that time Prince George and Princess Charlotte messed around at their dad's polo match to Meghan Markle's adorable page boy, there's no shortage of amusing moments from the youngest royals.
At Trooping the Colour during the weekend, Savannah Phillips (daughter of Princess Anne's son Peter Phillips) was spotted putting her hand over Prince George's mouth, as well as telling him to shush.
The pair were having a lot of giggles at the occasion to mark their great-grandmother's 92nd birthday along with fellow cousins Princess Charlotte and Isla Phillips.
'Savannah pretended to conduct during the national anthem was playing, and George joined in the fun,' a source told PEOPLE.
'When Savannah realised it was probably not what they should be doing, she stopped George from saying any more.'
It seems the moment is something of a family prank; throw back to 1990 and photographs show Prince Harry doing exactly the same during a Buckingham Palace balcony appearance, aged six.
Can you guess which fellow young royal in the picture is his unlucky victim?
It's Harry's then two-year-old cousin, Princess Beatrice.
Known for being a bit of a cheeky child, it comes as no surprise that Prince Harry pulled the hilarious stunt on the balcony – and it seems his cousin Savannah has inherited his sense of humour.
We wonder if the prank is known as 'pulling a Harry' within the royal family?
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