Townshend once called 'Pinball Wizard' "the most clumsy piece of writing [he'd] ever done"; nevertheless, the song was a gigantic commercial success and one of the most recognized tunes from the opera ... The song was introduced into Tommy as an afterthought. In late 1968 or early 1969, when The Who played a rough assembly of their new album to critic Nik Cohn, Cohn gave a lukewarm reaction. Following this, Townshend, as Tommy's principal composer, discussed the album with Cohn and concluded that, to lighten the load of the rock opera's heavy spiritual overtones (Townshend had recently become deeply interested in the teachings of Meher Baba), the title character, a "deaf, dumb, and blind" boy, should also be particularly good at a certain game. Knowing Cohn was an avid pinball fan, Townshend suggested that Tommy would play pinball, and Cohn immediately declared Tommy to be a masterpiece. The song "Pinball Wizard" was written and recorded almost immediately.That explains something that's always bothered me about Tommy: the cognitive dissonance of (as per the film) a narrative evidently about post WW-II trauma and the cults and spiritual journeys of the 1960s nevertheless seems to position itself so firmly as being (on the original album) about post WW-I trauma, and the run-up to Nazism and WW-II, something dated quite precisely by the second song, '1921'. Although Tommy seems so completely a product of its age, and although the film has I suppose overwritten our memories of the original, this latter makes it a much more interesting text I think.
But pinball (a postwar phenomenon; prewar it was more likely to be coin-operated versions of bagatelles, now known as "marble games" or "pin games") really doesn't fit this careful chronology. I'm not sure whether that disorientation is a good or bad thing.