David Schwimmer is "so thoughtful about everything he does"

She told SFX: "I don't you think ever get Schwimmer with just a, 'Yes, I'll do it.' He is so thoughtful about everything he does.

"Part of casting is you're also making sure that this is a relationship that goes both ways."

She revealed the 58-year-old star had "smart" questions about his role and the show as a whole, and he threw himself into his alter ego.

He added: "Right away, David's questions were so smart about the character and about the show. His ideas and suggestions were so smart.

"And he got really into researching botany [the character's science speciality], which was cool."

ex ecutive producer Rob Letterman explained how David's experience as a director and filmmaker was a massive help for the team.

He said: "He's also directed and he's a storyteller, so he really came at it at a very high level, which was very helpful for us with our crazy schedule.

"I mean, this is a hard show to make because basically each episode is a movie. It's hard to amortise anything across it, so it's always run and gun."

David is a huge fan of the genre, and he recently admitted that was a big part in him signing on.

He told Collider: "I was immediately intrigued. And then, I read the script and talked to the writers, and I learned about the really, really deep, dramatic backstory, as well as where it goes in the series.

"I was genuinely excited. I went and read the book that my character is inspired by, 'Stay Out of the Basement', about a botanist dad who starts to change, and I was like, 'Oh, this is gonna be so much fun.' "