First this guy's swordfighting with his non-dominant hand, then that guy's swordfighting with his non-dominant hand. Is anyone fighting on the up-and-up around here?

It's one of the greatest, most exciting reveals in movie history (well, in comedy movie history, anyway). Just when it looks like Inigo's going to bite it, he springs a little surprise on Westley and fights off his opponent. Then, when things are looking grim for Wes, he returns the favor and, of course, gets the best of the Spaniard.

It makes for a fun, funny, and unpredictable sequence, sure—but it also points up a big theme in the film. Eeeeeverybody's got a secret. Humperdinck's keeping it secret from Buttercup that Westley's still alive (and that he plans to kill her). Westley keeps his identity a secret from his true love (for a time). Even Yellin, Humperdinck's chief enforcer, is pretty secretive about that key he's been put in charge of. Amid all the swashbuckling, there's plenty of mystery, and it's part of what keeps us so engaged in the story.

It also helps prepare us for twists later in the film, and makes them not seem so out-of-left-field. Westley dies, but he's brought back to life. Inigo seems to have been killed, but he somehow survives. Because we're painted the tableau of a world where things are not always as they seem, we're kind of mentally prepared to suspend our disbelief in a few spots.

Like with the Impressive Clergyman. Like anyone could ever get a gig like that in a major kingdom with such a speech impediment.