Wee Willie Winkie runs the town in his nightgown, checking every child is in bed by eight o'clock. A proper bedtime classic, and one of the most enduring lullaby-adjacent rhymes in the language.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
Wee Willie Winkie runs through the town,
Upstairs and downstairs, in his nightgown;
Rapping at the window, crying through the lock,
"Are the children in their beds? Now it's eight o'clock."
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition