In Star Wars, two characters have shown up in almost every film (ten out of eleven theatrical releases) – the humanoid droid, C-3PO, and the astromech droid, R2-D2.
Both of these droids always seem to find themselves at the center of the plot – R2-D2 stores the death star plans, recruits Luke and Obi-Wan to the hero's journey, overrides security systems at just the right time, and seems to guide the main characters to the next step.
A MacGuffin is an object of plot importance and desire - usually, it carries a message, a power, a secret, or something of great importance. MacGuffins have been a mainstay in both movies and storytelling for centuries — from the Holy Grail in the Legend of King Arthur to the briefcase in Pulp Fiction to R2-D2 in most of the Star Wars films.
The term was made famous by Alfred Hitchcock, who described it as,
It might be a Scottish name, taken from a story about two men on a train. One man says, 'What's that package up there in the baggage rack?' And the other answers, 'Oh, that's a MacGuffin'. The first one asks, 'What's a MacGuffin?' 'Well,' the other man says, 'it's an apparatus for trapping lions in the Scottish Highlands.' The first man says, 'But there are no lions in the Scottish Highlands,' and the other one answers, 'Well then, that's no MacGuffin!' So you see that a MacGuffin is actually nothing at all. — Alfred Hitchcock
George Lucas said this about his version of MacGuffins,
that the MacGuffin should be powerful and that the audience should care about it almost as much as the dueling heroes and villains on-screen. – George Lucas
MacGuffins are interesting to think about in the context of narratives — what else can logically drive the plot forward, motivate the protagonists (or antagonists), and provide a source of tension and conflict without making too much of a statement on its own?