The 30-year-old actor stars in Clooney's new movie 'The Ides of March' - which he stars in, co-wrote, produced and directed - and he was amazed every day when he came to work to see how much energy the 50-year-old Hollywood hunk had.
Ryan said: "It was impressive to watch someone do so much. He's a superhuman person. I don't think I could ever multi-task like him. He's the writer, producer, director, star on 'The Idea of March'. And he's got practical jokes going on all the time."
The 'Drive' star has nothing but praise for George as a director and insists he did everything he could to create a calm shooting environment for the cast, which included Paul Giamatti, Marisa Tomei, Evan Rachel Wood and Philip Seymour Hoffman.
He added: "I'm sure it's very stressful but he actively ensures you don't feel any of that stress, so the atmosphere is great."
In the movie, George plays Democratic Presidential hopeful Pennsylvania Governor Mike Morris who is embroiled in sex scandal, while Ryan portrays Stephen Meyers, the mastermind behind Morris' campaign.