Mark Twain's 'Mysterious Stranger'

A literary precursor to ''E.T.'' is finally coming to television.

Not only that, it has only recently come to print in its more-or-less original version.

Mark Twain's ''The Mysterious Stranger'' was first published posthumously in 1916, pulled together by his publishers from the first and last of at least four versions he had attempted to complete. It was not until 1963 that a professor studied the original manuscripts at the University of California, a fact resulting in the publishing of the story as, presumably, Mark Twain himself wanted it to be read.

Now Julian Mitchell has adapted that most recent version for ''Great Performances,'' and it is being presented by Nebraska ETV Network in association with WNET-New York: The Mysterious Stranger (PBS, Monday, Oct. 11, 8-9:30 p.m., check local listings, since times and dates vary). It is medieval fun and games.

The mysterious stranger is a boy named 44, who, in a long daydream sequence, appears among the apprentices of a printing plant in medieval Austria. There he befriends our hero, a young Hannibal, Mo., printshop apprentice who finds himself daydreaming this medieval life. Our electronic extra-terrestrial is immediately catapulted into competition with the local alchemist-conjurer, who performs magic (but not black magic). 44 does everything better, but he gives credit to the alchemist as his master.

In typical Twain fashion, the story pokes fun at everybody in sight, questions everything in society, comes up with solutions perhaps more puzzling than the problems. But enroute, everybody has a jolly good time.

Before our hero returns to the reality of Hannibal, his friend 44 informs him that life is itself a dream. When our hero asks what he can do in a world without 44, he is told to dream other dreams, better dreams.

Sumptuously produced by William Perry, naively directed for the amazement of children by Peter H. Hunt, ''The Mysterious Stranger'' is an ironic, irreverent, extra-terrestrial Twainian romp.