Is there any question more difficult to answer than the request to boil your favourite show down to a single sentence?
Selling Mad Men to someone on the basis that it's about advertising executives is a tall order, as is convincing conservative relatives that a show about drug dealing is one of the great cultural milestones of the century.
Everyone's had that conversation which ends with a mumbled assurance that they'll check it out sometime while you wail, "But it's really good!" It's even more difficult to encapsulate all the depth of a TV series in a quick sales pitch when it doesn't only alter its tone, characters and style during its time on air, but also its most basic premise.
Long-running shows have a tendency to change over the years, but this article includes only those for which the original summary actually became inaccurate, for better or for worse. Spoilers abound, so be warned.