Now everybody has a smartphone in their pocket, there's an easy way to document that chance meeting with your favourite actor or singer.
Here are 16 of the very best.
1. Gerard Butler
Margaret Shevlin took the opportunity to grab a snap with the Scottish star at Edinburgh Airport while waiting to pick up her aunt from the same USA flight. Photo: UGC
2. Simon Pegg
Kenneth Syme met actor Simon Pegg at the Empire Leicester Square, in London, for the premier of his film 'Paul'. Photo: UGC
3. George Ezra
Singer George Ezra was filming a music video in New York's Central Park when Lauren Conway bumped into him. Photo: UGC
4. Lewis Capaldi
Debbie Henderson and Susie Ritchie had a great night meeting the chart-topper in an Edinburgh pub in 2019. Photo: UGC