On Wednesday's episode of The Late Show, Stephen Colbert tasked Ian McKellen and Helen Mirren with a dramatic reading of the key line from President Donald Trump's phone call with Ukrainian President Volodymyr Zelensky.

The conversation, in which Trump urged Zelensky to investigate the DNC and former Vice President Joe Biden, a leading 2020 Democratic presidential primary candidate, has led to an impeachment inquiry against the president.

Colbert explained that Trump wants people to read the transcript out loud in the hopes that "it will suddenly seem so innocent that you won't want him removed from office." In order to test that theory, he recruited McKellen and Mirren.

"The scene is, you're on the phone with the Ukrainian president. His country's been invaded by the Russians. You've got the military aid he needs, but you're not going to give it to him unless you get the pro quo back. This is what you say after he says, 'I would like the javelin missiles,'" said Colbert before he asked Mirren to read the line "casually."

Mirren leaned toward Colbert and said in a quiet tone, "Zelensky, I'd like you to do us a favor though." Colbert tapped his gavel on the desk and declared that Trump was guilty.

McKellen read the same line, though made a gun gesture with his hand as he addressed Zelensky.

Colbert next asked Mirren to read the line again, though with a happy tone, and asked McKellen for "innocent."

When none of the different readings of Trump's request for a favor satisfied Colbert, Mirren agreed with his verdict. "There's no way of saying that any other way except for guiltily," she said. "It's a guilty phrase." 

Earlier in the interview, McKellen spoke about his upcoming role in Cats. The actor stars in the film as Gus the Theatre Cat.

While many members of the star-studded cast went to "cat school" to learn how to move and act like their feline characters, McKellen said he didn't participate. "I didn't bother going to school," he said. "I just found my inner pussy."

"The point is these are actors who are playing cats, they are not cats," he explained of why he chose not to attend the classes. "We walk on two legs rather than four, for example. And I promise you, Judi Dench does not have a tail. Nor do I."