Something you might change on a bed

DIAPER

Think of what parents often replace after a baby wakes up from a nap—it’s not the blanket or pillow.

The clue plays on the double meaning of "change" here—it can mean altering something or replacing it, like swapping out bedsheets, but it also refers to changing a baby's diaper. Since a diaper is something you routinely change and is associated with beds (like a changing table or nighttime use), the answer fits neatly. The wordplay relies on the everyday task of diaper changes, making it a clever but straightforward hint.