Officers say alarmed drivers started calling in about seeing a child holding up a sign that read "help me, she's not my mom! Help!".
CHP officers, as well as a K-9 unit, pulled the car over in Stockton only to find out it was a prank by the child, and the mother had no idea the girl had made the sign.
"This is a reminder that parents need to be aware of what their children are doing in the back seat at all times," said officers.
CHP says six units responded to this call instead of responding to legitimate calls or patrolling their beats.