The Prisoner: In the final episode when Number Six defeats Number Two, every time he tries to speak, he's drowned out by a chorus of "I, I, I,..." Represents the result if everyone follows his lead and cares only for their own individual expression. - Jove Hack
And you notice what a difference a comma makes when almost every episode begins with 'Who is Number 1?' 'You are Number 6.' and you realize it could easily be 'Who is Number 1?' 'You are, Number 6.' - Garrison Skunk
And, of course, "I" is also a Roman numeral...
...chanted six times whenever he mentions the word.
The episode "Hammer Into Anvil" gets deeply philosophical. Number Two quotes Goethe ("You must be Hammer or Anvil"), identifying himself as the Hammer who is going to pound on Number Six until he breaks. Number Two apparently never studied his George Orwell; Orwell pointed out that the Anvil is actually stronger than the Hammer. You can whack an Anvil with a Hammer all day and never break it; in fact, you might just break your Hammer in the process. This is exactly what happens to Number Two over the course of the episode: he becomes the Hammer, and shatters on the indestructible Anvil that is Number Six. Number Two was a poor student of philosophy. And blacksmithing.
In the title sequence, on his way to resign Number Six leaves the parking garage through doors labelled "way out".