"…Very early in [Keaton’s] movie career friends asked him why he never smiled on the screen. He didn’t realize he didn’t. He had got the dead-pan habit in variety; on the screen he had merely been so hard at work it had never occurred to him there was anything to smile about. Now he tried it just once and never again. He was by his whole style and nature so much the most deeply “silent” of the silent comedians that even a smile was as deafeningly out of key as a yell. In a way his pictures are like a transcendent juggling act in which it seems that the whole universe is in exquisite flying motion and the one point of repose is the juggler’s effortless, uninterested face.
Keaton’s face ranked almost with Lincoln’s as an early American archetype; it was haunting, handsome, almost beautiful, yet it was irreducibly funny; he improved matters by topping it off with a deadly horizontal hat, as flat and thin as a phonograph record. One can never forget Keaton wearing it, standing erect at the prow as his little boat is being launched. The boat goes grandly down the skids and, just as grandly, straight on to the bottom. Keaton never budges. The last you see of him, the water lifts the hat off the stoic head and it floats away.
Keaton worked strictly for laughs, but his work came from so far inside a curious and original spirit that he achieved a great deal besides, especially in his feature-length comedies. He was the only major comedian who kept sentiment almost entirely out of his work, and he brought pure physical comedy to its greatest heights. Beneath his lack of emotion he was also uninsistently sardonic; deep below that, giving a disturbing tension and grandeur to the foolishness, for those who sensed it, there was in his comedy a freezing whisper not of pathos but of melancholia. With the humor, the craftsmanship and the action there was often, besides, a fine, still and sometimes dreamlike beauty.”
—James Agee on Buster Keaton, from his legendary 1949 LIFE magazine piece, "Comedy’s Greatest Era"