The Duke and Duchess of Cambridge got involved with a session of the Older Yet Wiser project during a visit to Bradford.
The project supports grandparents with child-caring responsibilities.
As the group sang the “banana song”, Kate picked up 18-month-old Sorayah Ahmad and danced with the youngster, helping her shake her rattle in time with the music.
The duchess then helped the smiling little girl to play a game of peekaboo.