More like the Number Of the Beast.
I spy - a reader of Heinlein! One of my favorite writers, even if he did get weird towards the end of his life.
This was even better than the excellent short (which title I cannot recall) about all the different Clark Kent/Superman incarnations trapped in one room for a few hours. Or the one about all the different Lex Luthors (which title I also cannot recall) stuck on an island together comparing psychoses and trying not to get killed by each other.
Very nice, especially the end where Smallville-Clark almost remembers the line about openly becoming a flying protector. Nice going, you infinitive-splitter you!