Interestingly, Merle Haggard's "act" was in some ways similar to Mark's in that every show was almost exactly the same - even the jokes didn't change! Still though, Merle's charm and the strength of his band easily made up for the lack of spontaneity.
"Ladies and gentlemen, I'd like to introduce the strangers"- I must admit, I never tired of that one. Snuck in to soundcheck once and actually got to meet Merle and the Strangers. They let me stay and I watched the Dylan's band playing the studio version of Hazel on a boom box and arguing about the chords. Tony won and they brought it out that night. sweet.