It's interesting, the kind of small but glaring errors that take you out of something.
Mad Men has an absolutely fantastic crop of writers, editors, directors, and actors -- so it's jarring when not one of them notices that, say, "1960, I am so over you" is a phrase that no human being has ever uttered. It's one thing to use a 1963 Bob Dylan song as background music in an episode set in 1960; it's another to actually have a character use slang that would be out-of-place in a show set in 1990.
A less severe but still amusing flub: in last week's Thundercats, a character said he had worked his math out to "the thousandth decimal point". I think I can see the error in his calculation: he used more than one decimal point.
Also: I changed the name of the "toons" category to "cartoons", because this is not Who Framed Roger Rabbit? The only reason I used the shortened form of the word in the first damn place was for a set of link banners I made back in 2000 that only one guy ever actually used.