Heil Honey, I’m Home was a short-lived British sitcom which aired for only one episode on Galaxy. It covers the fictional home life of Adolf Hitler and Eva Braun in the style of 50s sitcoms (vacuous dialogue, canned laughter, etc.) The program provoked some controversy when it first aired, and is still the only British television program to be cancelled after only one episode. After watching the first episode, I can see a lot of reasons why it was cancelled, but not a single reason why anybody thought it was a good idea to make the show in the first place.
mental_floss has a list of a few more TV shows cancelled after only one episode.