Prince William has been previously heard referring to Prince George as ‘poppet’ too.
Fellow shopper Sarah Daniels revealed: "As I was looking at the shelves I noticed a tall dark-haired lady further down the aisle and thought to myself 'I recognise that face'. Then I heard George say 'Charlotte, pick that up' and the penny suddenly dropped as to who they were. It seemed like a lovely family outing for them the day before Christmas Eve."
Sarah also revealed little George asked mum if he could purchase some slim. The royal family bought pictures, children's books and art materials at the tills.
The royals are known to open their presents on Christmas Eve.
"The British royals still follow the German tradition of opening presents on Christmas Eve,” said royal historian, Marlene Koenig “The members of the family who are present at Sandringham exchange gifts, usually not expensive. The gifts are put out on a trestle table after tea time."
Marlene added that it is most likely that the children will also open presents on Christmas morning at Anmer Hall, which will be from Santa.