Christopher Nolanhad a Shakespearian moment when he came toThe Late Show.

Ive always wanted to work with him.

Ive always seen that in his work, Nolan said.

(L-R) Christopher Nolan and Robert Downey Jr.

(L-R) Christopher Nolan and Robert Downey Jr.Matt Winkelmeyer/Getty Images

And he has such charisma as Tony Stark.

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Youre looking for some kind of generosity.

He has this incredible generosity of spirit.

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Hes helping them clarify those emotional connections.

It wasnt always such a love connection between Downey Jr. and Nolan.

The role of Dr. Jonathan Crane, the Scarecrow, would ultimately go to Downey Jr.sOppenheimerco-star,Cillian Murphy.