What would the Grinch do if he caught a driver being naughty?

Some drivers in the Florida Keys who exceed the speed limit in school zones found out firsthand when they ran into the gloomy green creature and were given a surprising choice.

An officer dubbed the Florida Keys "Grinch cop" is dressing up as the famous character from the book by children's author Dr. Seuss in an effort to get drivers to follow speed limits and stay off cellphones in school zones.

While in his Grinch suit, Col. Lou Caputo works with other deputies to clock drivers in school zones in Key Largo. The officer’s antics were captured in a video posted Thursday by the Florida Keys and Key West tourism board.

Confronting an allegedly misbehaving driver, Officer Grinch tells the surprised man behind the wheel, "We're going to give you a choice between a citation and an onion.

"Now I know you want to think about it, but make a wise choice. The citation's a little expensive. You weren't going too fast but it's enough for us to pull you over."

The driver in the video continues smiling as he accepts the onion, and Officer Grinch tells him -- nicely -- that police want him to slow down next time.

"It's for those not paying attention going just over the speed limit," Caputo later said in the video, explaining the thought behind the choice. "We want to make them aware that we want them driving safely through the school zone in the holiday season and at all times."

Caputo said he started the Officer Grinch program more than 20 years ago to encourage drivers to slow down in the school zone while adding some humour with an attention-getting outfit. The choice – ticket or onion – was inspired by Jim Carrey's onion-loving character in the 2000 film “How the Grinch Stole Christmas.”

"All drivers in 20 years have always taken the onion. Tickets are expensive, but who would turn down an onion you can use for deodorant? You can eat it, you can play with it -- an onion is perfect," he joked.

While it’s a light-hearted approach, police do check vehicles' licence plates and drivers' licences before making the unusual offer, he added.