Failing to see the last episode of a tv-series season, and instead start to watch the next season. Might occur when failing to count the number of discs in a DVD-box, or failing to download a complete season.
A: Damn, I failed the finale of 'How I Met Your Mother' season 3 last night.
B: That must really suck for you, since it's no use watching the finale now that you know that Ted (... insert spoiler) in the end of it.
A: Well, I realized that I had finale failed and managed to turn it off before that was revealed in the prologue of the first episode of season 4, but thanks.