One of the things I think shows the mark of an outstanding series is when - years later - people at parties talk about the individual episodes in terms of "the one with..."

So people who watched Doctor Who as kids talk about "that one with the giant maggots", or "the one with that ventriloquist's dummy that came to life". I found it really funny years ago when Sonia and I were first dating, and since she was born in 1981 she had these childhood memories of "the one with the creepy clown and the kites" and "the one with the monster made of liquorice allsorts".

This theory is one of the things I liked about Friends, since every episode bar two is titled "The One with..." or "The One where..."