Now that's a classic, I imagine I could find it somewhere but basically Welles was asked to deliver the line "In July" as "IN July," (as opposed to "In JULY,")and Welles really flips out because its totally unnatural to emphasize "in" in that sentence.
In his case he wasn't going to suffer a fool. Shatner is just having fun with a guy who doesn't have the stones to stand up to him. Or, instead of giving him the delivery he wanted, change the direction if its not getting the response, like saying "bigger smile" will get you into "more excitement". Shatner sounds like he's smiling only when the tape isn't running.