Now everybody has a smartphone in their pocket, there's an easy way to document that chance meeting with your favourite actor or singer.
We asked readers on our Facebook page for their starriest shots and were inundated with famous faces.
Here are another 18 of the very best, in the third of our picture galleries.
See the first part here.
See the second part here.
13. Courteney Cox
Fraser Ogilvie grabbed a snap when he bumped into the Friends actress. Photo: UGC
14. KT Tunstall
Eoin Klein reckons "nothing beats homegrown talent" after posing with the Fife singer. Photo: UGC
15. Ricky Hatton
Gary Docherty was holidaying in Tenerife when he took the opportunity to get a picture with the boxing hero. Photo: UGC
16. Andy Serkis
Sophie Milner-Smith said the Lord of the Rings actor "couldn't have been friendlier" when she and her son Gordon met him during a tour of Edinburgh University. Photo: UGC