There are loads of versions.
Basically the story is some people go on holiday. While they are away, one day they go back to their hotel room only to find they have been burgled. Strangely, their camera and toothbrushes haven't been taken. They replace some things but carry on using their toothbrushes. When they ge home, they have the film developed. One of the pictures is the burglars mooning with tootbrushes sticking out of their backsides
Obviously this is pre digital