But how did the royal photographer get the two-year-old to crack out such a cheeky grin at just the right moment?
"The whole shoot went swimmingly well," photographer Ranald Mackechnie said.
When asked what made Prince George so happy, he said: "Me! Me making strange faces or putting my hands up on my head."
Watch the video above to see the funny poses Mackechnie pulled to get the perfect shot.