Opening sequences are something (I think?) common to all television series. On a basic level, they tell you what you’re watching and who is in it.
But, if effectively used, they can really add to the series, and the episode, they are attached to. The best opening sequences lodge themselves in the mind, becoming inseparable from the series itself in the same way as cover art on a book. Just look at the Friends opening sequence.
So here’s something I’ve been musing on for a while, pushed to crystallisation by a recent io9 article. My personal top five TV opening credit sequences.