Retcons suck! Well, sometimes they do. Retcons are a way for writers to overlook established facts about a character if it serves the interest of the current story. The problem is that when you're a serious fan, such a casual disregard for continuity can be annoying. Especially when it comes out of nowhere and makes little to no sense.
When people say retcons, they think comic books or maybe sci fi. But even sitcoms have been known to rewrite their own history for no good reason. Once in awhile it is ok. Like when The Huxtables went from four children to five. Or on Will & Grace when Karen's maid suddenly went from not understanding a word of English to speaking it fluently. Sometimes these changes are ignored, other times they are acknowledged with one simple line of dialogue. Here now are five examples of when a show changed established continuity for no good reason.
The Golden Girls
This isn't a huge one but is worth noting. On this series Rose had a long term relationship with a man named Miles. He was a teacher and appeared several times. Then at one point, for some reason, the writers decided to mix things up. It was suddenly revealed that Miles was actually an informant for the FBI, currently living under the witness protection program. When Miles has to flee, this causes a crisis for Rose. A crisis that only lasts a few episodes when Miles returns and the mobster after him is captured. This was obviously a cheesy way to shake up Rose's story for a season, and the whole thing is quietly forgotten the next year. What makes it even worst is an earlier episode involving Miles overprotective daughter. A daughter who is of course never mentioned when the whole informant stuff comes up.