Kate was talking to a student, Shannon Hunt, when she made the joke, and also said that the little boy can "get a bit grumpy on the long flights."
Prince George is being looked after by his nanny, Maria Teresa Turrion Borrallo, while the Duke and Duchess of Cambridge attend royal engagements and Kate also admitted to missing her little boy while she has been busy.
Kate also said that George is "changing so much" while they have been away.