First up is Cartoon Kay, from the 1963 Disney animated version of TH White's The Sword in the Stone. White's book and its sequels are, for me, far and away the greatest version of this very old story, full of pathos and humour and imbued with one man's righteous fury against the dreadfulness of humanity as a species. The film encompasses none of these things, but then it doesn't try to. It's an efficiently amusing cartoon for kids, in which a young Arthur - or Wart - gets turned into various creatures by Merlin, with the occasional sing-song and dancing teapot thrown in.
Arthur's older brother, Kay, is one of the most obnoxious depictions of Kay since Malory showed him slapping a woman to get Sir Percival's attention. This Kay is not only an unpleasant bully who makes Wart's life hell, but dumb as a post.
Next up is Sexy Celtic Kay, from the 1970s series Arthur of the Britons. Made by HTV between 1972-3, this series was an interesting but flawed experiment, the first screen version of the legend to make an attempt at placing Arthur and his followers in a believable historical context i.e. post-Roman Britain. The warlord Arthur and his men are just a bunch of grubby Celtic warriors living in thatched halls and roundhouses, though they do have fabulous hair - none more so than Michael Gothard as Kay (Kai).
Screen Kay no.3 is my personal favourite. Played by Niall O'Brien, Sir Kay in John Boorman's Excalibur (1981) plays a subtle but important role in the film. Boorman clearly did his research on the character, and allows Kay his proper place as Arthur's loyal seneschal, a constant and dependable presence when all the other knights are falling to bits (quite literally, since they never take their armour off. That stuff rusts).
This Kay remains by Arthur's side when the rest of the knights ride off on the doomed Grail quest, here reinvented as an almost pagan symbol of fertility and renewal. A hint of his obnoxiousness remains, such as when he says to an aspiring young squire: "kitchen knives and greasy spits will be your weapons, boy - to the kitchens!" but otherwise he is a decent, upright sort of chap.
The fourth and last of my Screen Kays is sadly the worst. Played by Peter Mooney in the ill-fated Starz series Camelot - or Hack n'Shag, as it might have been called, such was the degree of naked tits and softcore humping on display - this Kay lands with a dull thud. Mooney is one of those routinely handsome actors that seem to populate all modern fantasy/sci-fi shows, and his character is as boring as his haircut. Not a whit of Kay's traditional nastiness remains. Without that, and without much natural charisma from the actor playing him, Kay is reduced to just another knight, though he keeps his role as Arthur's foster-brother.
So far as I'm aware, no more Arthurian films or televised dramas are planned for the near future, though doubtless there will be: one recent idea, apparently shelved, was a remake of Excalibur. Hopefully, the next time Sir Kay appears onscreen, he will be in his full glory as an obnoxious, sarcastic asshat capable of breathing underwater, shooting fire from his hands, killing oxen with a single blow and shooting up to the height of a tree. At least it would be good for a laugh.