George is pictured in the arms of his dad, Prince William, in the photo snapped by Mario Testino on July 5 at the Queen's Sandringham estate during the family's celebration of Princess Charlotte's christening.
George, dressed in the smocked set by one of mom Princess Kate's favorite children's wear designers, Rachel Riley, shows off his adorably toothy grin – and "little monkey" attitude – in the picture.
"This photograph captures a very happy moment on what was a special day for The Duke and Duchess and their family," says a spokesman for Kensington Palace. "They are very pleased to share this picture as they celebrate Prince George's second birthday."
The birthday boy – otherwise known as the King of the GIFs – will no doubt be wearing something different (and arguably more practical) for the rough-and-tumble of his party at home at the family's country home, Anmer Hall, where the Royal Fab 4 will be "spending the day privately in Norfolk," a palace source tells PEOPLE.
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