I thought
this clip from a German TV show was very funny. It explains the setup right at the beginning, so no harm doing so here: a cloakroom with a mirror, except it isn't a mirror, it's plain glass with an exact mockup behind it, and a set of well-choreographed identical twins. It's the way they all plaintively say things like "Sehen Sie mich im Spiegel?"... and the woman with the glasses who eventually concludes that she must come from another planet. Good thing there's no-one else working in my office.
Ah well, it's nearly time for a coffee.