"What was he smoking?" is often just a joke when someone does something bizarre.

But consider the case of a man arrested in Old City for offering a cabbie a substitute for cash.

Michael Medvec, 23, allegedly tried to pay with a bag of marijuana.

While police were at the scene.

"The cops were only a couple of feet away," Sixth District Capt. Brian Korn told Philly.com.

Officers stopped because the taxi was double parked Friday night on Chestnut Street, and learned that a guy who owed about $8 left his phone to assure the cabbie he'd be back with cash, Korn said.

When the fellow returned, he had the nerve to tell police something like, "You have to leave," Korn said.

The driver even offered to forget the fare, when Medvec allegedly offered his herbal remedy.

"The cab driver didn't want any part of it," Korn said.

Even though it was hardly a major crime, the officers felt compelled to act.

"It's right there in their presence," Korn said. "They can't ignore it. ... You do something silly, you need to get spanked a little."

Medvec wound up under arrest, charged with marijuana possession, according to court records, which describe him as Caucasian with black hair and green eyes.

Medvec was released on his own recognizance Saturday, and faces a status hearing Monday.

Korn said he'd never heard of a similar case in 33 years on the force.

He felt sorry for the driver, who might have to miss work to appear in court, he told CBS3.