Ewan McGregor:
The passer-by whom Daniel Feeld overhears quoting lines from his script is an un-credited McGregor who had appeared in another Dennis Potter play, Lipstick on Your Collar (1993), 5 years earlier.
In the Dennis Potter interview "Seeing the Blossom", Dennis Potter comments that he wrote "Karaoke" and its sequel "Cold Lazarus" based on the simple writer's premise: "If you wanted to make the world a better place, who would you kill?"