Taking Care of Terrific(1988)

14-year-old Enid Crowley hates her name and everything about her boring life. All this changes when she becomes a full-time babysitter to a sheltered boy. The two hook up for some hilarious adventures in the park with a mysterious bag lady and a street musician. With the help of Enid's boyfriend, Seth, they try to give the park dwellers a "special evening," but their good deed backfires and lands them in trouble.