I got to direct Leonard Nimoy once.
I was a writer-producer on a prime time animated series named Invasion America, for Steven Speilberg and Harv Bennett. Harv managed to convince Nimoy to do a limited run as a character. Nimoy agreed, provided that he'd be in and out.
So, of course, Steven didn't like the performance. Nimoy, who was only supposed to be there for four episodes, kept being brought back to do the role again. He tried to be gracious, but it was obvious he wasn't enjoying himself.
So one day we were working our asses off trying to get a reading, and we just couldn't get it the way we needed it from him. It was a short line, which means it's actually harder to get the reading right. We didn't want to just give it to him, cause that would be like saying you can't act. But he was getting increasingly surly.
So we're in the booth, trying to think of a way to get the read from him. Then I had an idea. I opened the mike and said "Lee, gimme the line and raise one eyebrow while you read it."
He nailed it, one take.