Willis did end up pulling double duty on Moonlighting and Die Hard at first.
“So after the first week,” screenwriter Steven E. de Souza told Slash Film in 2018, “John McTiernan came to me and said, ‘We have at least another week of this overlap. Why don’t you go back into the script and see if you can find more stuff for all the other characters to do?’
“That led to more scenes at the house with the housekeeper,” he explained, “it led to building up the idiot newscaster, and it led to some of the great scenes between Holly and Hans Gruber.”
Moreover, de Souza continued, “Powell was always in there, but under that direction, I ended up giving him more interaction with the cops on the ground, and there was some comedy that came out of that.”
The 11th-hour additions to the dialogue necessitated a bit of improvisation from the actors and a lot of last-minute memorization. Willis credited his Moonlighting experience, while VelJohnson attributed his stage work for his ability to go with the flow.
“For a young actor,” he told E!, “the stage is the most telling classroom that you could ever have…Theater gives you a certain discipline that you don’t get otherwise. It teaches you how to deliver.”