In J.M. Barrie's Peter Pan, who is it that must sleep in a cradle?
When Wendy goes to live with the lost boys, she becomes their mother and cares for them in every way. Though she fears she does not have the qualifications, she quickly takes on the responsibilities that a mother would, including darning their socks and scolding when necessary.
They have many adventures, and Wendy is always there to keep house for them and tell them stories.
One thing Wendy does is tell Michael he must sleep in a cradle. He feels he is much too old for this, but Wendy says their home must have a cradle and he is the smallest of the boys, so he must sleep in the cradle.
While the Darling children are in Neverland they play a game of house. Wendy is the mother figure, Peter is the father, and all of the lost boys are the children. A family isn't complete without a baby and since Michael is the smallest of the boys he is made to sleep in the cradle and play the role as baby.
"But Wendy would have a baby, and he was the littlest, and you know what women are, and the short and the long of it is that he was hung up in a basket."- Peter and Wendy