There's a concept from early Russian formalist theory, "Skaz," which refers to the ability of a supposedly invisible and objective third person narrator in fiction to use slang and other personal phrasing to reflect something about the character or situation being described. The term (which literally means "speech") might be translated as "talkitiveness"--we'd say "voice" today. It's a bit like breaking the fourth wall that supposedly separates the storyteller from the audience. Of course the technique in a script has to be pinned to an enthralling story--otherwise the writer becomes a slave to convention, not an innovator (like the numerous Shane Black imitators in spec scripts from the 90's).

I love the visual cues in the example from Cobweb.