In The Truth, William is struck by the press, which leaves its msrk on him. When he looks in the mirror, he sees a reversed R bruise on his forehead.
Of course it's reversed because he's looking in a mirror, but I've wondered for years - why an R? I think I may have guessed it.
(Also, there was a movie, Cool World, that had comics characters in an unreal world, "noids" (nerds) who wanted to live in the cool world, and "real" people who didn't want to live in a fantasy world. I'm not quite sure whether that movie came out before The Truth, but I think it did.)
In Red Dwarf, the hologram character has an H on his forehead, for hologram. There was a fad for fans of the show to wear an H. William is Real, so he has an R.