Writer of "The Doomsday Machine" confirmed that William Shatner counted lines on Star Trek

Over the history of Star Trek, many have said how difficult William Shatner was to work with, even though he was an excellent actor. The one thing said about Shatner, that has come up quite often, is his propensity to count lines in the script, ostensibly to make sure he got the most lines in each episode. While that seems ludicrous on its face value, apparently, it’s true. As in an interview included in Captains’ Logs The Unauthorized Complete Trek Voyages by Edward Gross and Mark A. Altman, the writer of “The Doomsday Machine,” Norman Spinrad verified the truth as he was actually on set when this had happened.

In the original version of the episode Spinrad wrote, Commodore Decker was much different. He had a stronger personality and wasn’t found in a daze barely hanging on in his ruined ship. Instead, the Enterprise away team found him looking out the viewscreen, and he was furious. But that type of character wouldn’t work because he could have potentially overshadowed Captain Kirk. So Spinrad had to take Decker down a few notches and reduce his lines in the episode. On top of that, some of the lines Spinrad had written for Spock were given to Kirk.

Spinrad was on set during the filming of “The Doomsday Machine,” and said “yes, he [Shatner] counted lines.” And the director was struggling because one Spock line had been taken out during a conversation between Kirk and Spock. That left no reaction that would make the next line work. So Spinrad suggested that Spock “grunt or something” because of the missing line.

In all fairness, though, Star Trek: The Original Series had barely eked out a second season so everyone was on edge, not knowing whether this would be their last. An actor making sure they got the most out of the script, while to many might seem egotistical, makes sense. They're already thinking about their next job, and that means they need more of their acting abilities to be seen onscreen. No, this didn't exactly make Shatner beloved by his fellow actors, but he obviously did something right as the Emmy award winner has gone on to have an extremely prolific career that has spanned seven decades.