What do the greatest cornerback of all time and a trash talkin' receiver have in common???

SMART CARS!!!

TMZ Sports has learned that ex-NFL stars Deion Sanders and Chad 'Ochocinco' Johnson just copped these custom-made SMART rides from Alex Vegas's Auto Firm in FL.

We're told Deion (well, Coach Sanders) decided to get a SMART vehicle when he saw Ocho cruisin' around in one ... and they're both pretty dope!

Check out Primetime's whip -- the glossy black with dark tints featuring his jersey number '21' on the grill and Prime on the trunk.

His nickname is even on the car tires!!

Johnson went with the matte black -- with his nickname 'Ochocinco' on the tires, too!

Even though they're small, these electric cars are filled with cool stuff -- including auto parking, automatic emergency braking and wireless charging docks.

And, they're pretty fast ... that's according to Ochocinco who was doing some spinnin' moves in his new whip Friday --- challenging anyone to see him on the streets.

"Doing doughnuts in the city in luxury," Ocho said on Instagram.

"900 horses under the hood, any of you Donk riders, Hell Cats, Trackhawk or Challengers want smoke bet whatever & I’ll pull up."