If you've ever been to a charity auction, you'll be well aware that experience afternoons such as a penalty shoot-out with David Beckham, a track race against Usain Bolt or a javelin-throwing lesson from Jessica Ennis-Hill can sell for upwards of £50,000.
So, imagine the look on the faces of two unsuspecting amateur tennis players in San Francisco on Sunday night when they were asked if they could add one more player to their game – that player being the World No.1 female tennis champion, Serena Williams.
According to Mashable, the American tennis star was out for a late-night stroll in San Francisco's Mission District on Sunday when she came across two men playing a game of tennis in Dolores Park.
Despite wearing a pair of fluffy boots and carrying her dog, Chip, the 23-time Grand Slam winner walked over to the pair and asked if she could play the winner of their game, much to their shock.
Serena shared a video of her surprise encounter on Snapchat, where she can be seen tightening the laces on her boots before the match, warning viewers: 'Don't do this at home'.
After the match, the newly-engaged sportswoman told viewers: ' So the moral of the story is you never know when I could be coming to a tennis court near you.'
Serena, we're ready for you.