“C” is for child endangerment.

A Pennsylvania mother was treated for overdosing while wearing a Cookie Monster costume — just minutes after dropping her 9-year-old daughter off at a babysitter, according to a report.

Rachel Love Martin, 38, of Westmoreland County, was charged Wednesday with child endangerment after leaving her autistic daughter at a babysitter’s home in West Newton, according to a criminal complaint obtained by KDKA.

The babysitter called cops because she was concerned Rachel Love Martin was high on drugs when the 38-year-old Westmoreland County woman dropped off her autistic daughter.

Responding officers found Martin wearing a Cookie Monster get-up and slumped over the wheel of her still-running car behind the babysitter’s home, the report said. The child was wearing no shoes or socks, despite temperatures being in the low 40s.

Cops administered Narcan because they believed she OD’ed on heroin, police said.

Martin was rushed to an emergency room — where she was later revived — as investigators contacted child welfare officials who placed the child in the custody of her grandmother, the station reports.

Martin was arrested and charged with child-endangerment and has been released after posting $10,000 bond.

It’s unclear why Martin was wearing the costume, police told KDKA.

A message seeking comment from West Newton police was not immediately returned Thursday.

Martin is due in court for a preliminary hearing on March 9.