User blog comment:Mikemacdee/Creepypasta Riffs/@comment-25024572-20150318105652/@comment-4715955-20150319021421

That's another thing that makes a cast of riffers useful: they can have dialogues to make fun of the characters, which makes adding lines to the story easier. You indicate who's speaking and who they're impersonating. The old school MST style is somewhat similar to broadcasting scripts.