When you get up and leave as the credits role at the end of the film, only to realise that there is actually another scene, so you stand awkwardly in the aisle until it finishes.
People who leave at 90minutes during a football match, only to miss potentially the most important part of the game.
Man 1: Did you see the Canadian GP?
Man 2: Only until it was rained off...
Man 1: You Dufus
, they restarted it, Button took Vettel on the last corner, Amazing
Man 2: Aww, no way!? I left to beat the rush.
Man 1: What rush? You were watching it at home...
Man 2: I needed to go out to buy a pickle
Man 1: I hope you realise what an idiot
you have been...