Serena Williams surprises random fans, challenges them to a match while on late-night stroll

Serena Williams' casual stroll unfolded into the match of a lifetime for two late-night tennis players.

While walking with her fiancé and Reddit co-founder, Alexis Ohanian, on Sunday night, the 23-time Grand Slam champion noticed a game between the two men and hatched a plan to surprise players by asking if she could swing with them.

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"I think they're in the middle of playing out points, but I'm going to ask them if I can have the winner," Williams said to her social-media followers via Snapchat as her beau Ohanian video-recorded the 23-time grand slam champion.

Williams appeared uncertain if the players recognized her initially -- but the pair was clearly taken by surprise once Williams and her yorkie, Chip, approached the fence to meet them.

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"Don't get tight!" Williams jokes, to which viewers can hear Ohanian laugh and say to her off-camera, "You're already trash talking?"

The trio posed for the photo afterwards. Williams, who wore boots throughout the pick-up match, concluded with a warning to her other fans out there:

"The moral of this story is: You never know when I could be coming to a tennis court near you!"'