Frances Tiafoe and Caroline Wozniacki hit the road for trivia with Cincinnati Open fans

With 125 years of tennis history at the Cincinnati Open, fans who've attended continuously over the years have no doubt learned a thing or two about the sport. But Frances Tiafoe and Caroline Wozniacki put that knowledge to the test this week as they climbed into one of the tournament's official vehicles to surprise fans with an impromptu quiz show.

As fans piled into the vans, they were stunned to see Tiafoe and Wozniacki already sitting inside, and the two stars greeted their guests with selfies, hugs and handshakes.

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That wasn't all that they had in store for their passengers. They tested their knowledge on key facts about the tournament and its players for prizes, including free ice cream and $50 of merchandise credit. Questions included the man who has won the most Cincinnati titles (it's Roger Federer, with seven); the tournament's age; and current events on tour.

How much did the fans know? Watch the video below to find out.

It's not the first time this year that a tournament has put players undercover as "men (and women) "on the street," nor is it the first time we've seen Wozniacki hitting the road in North America.

Remember in Indian Wells when Alex de Minaur played the role of a parking attendant, Ons Jabeur gave directions, and Daniil Medvedev sold merch? How about the hilarious hijinks that ensued when Wozniacki played "Uber driver" for Daria Kasatkina in Charleston, as chronicled on the latter's hit vlog?

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"Thank you so much for playing along," Wozniacki says as the fans depart her car. "You guys were so good!"

But we'd argue that she and Tiafoe were too.