Like many kids her age, the four-year-old apparently "loves unicorns".
The youngster was reportedly spotted with a sparkly charm in the shape of a unicorn when she arrived at Thomas's Battersea.
And now her doting dad has admitted she's a big fan of the mythical creatures.
Speaking on a visit to Harcombe House in Devon, William said: "My daughter loves unicorns. Loves them. Very cool."
Meanwhile, it has been claimed that Charlotte – who has brothers Prince George, six, and Prince Louis, 16 months – earned the nicknamed "Warrior Princess" during her time at nursery.
Charlotte attended Willcocks Nursery in London for 18 months and earned the nickname because of her "feisty" personality and "tomboy" nature.
My daughter loves unicorns. Loves them. Very cool.
Royal expert Katie Nicholl told Lorraine the princess would probably be called Lottie as she started school alongside her big brother, who is affectionately known at Thomas's as "PG".
Katie said: "The other nickname that she had when she was at Willcocks Nursery, which was up until just before the summer, was Warrior Princess."
She added: "I'm wondering if that might be a nickname that will stick with her. Apparently she earned that nickname because obviously she is a princess, but she's quite a tomboy."
Katie added that Charlotte "loves climbing trees and she's very much an adventurer".
She revealed: "She was quite known for her feisty personality."
As she started school, sources revealed that Charlotte was "so excited" to join her brother at "big school".
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