The Forrest Gump star and his actress wife Rita Wilson were thrilled when they were invited to a white-tie dinner at the monarch's London residence alongside U.S. President Barack Obama and First Lady Michelle.
Hanks received etiquette tips for interacting with the royals and wore his finest tuxedo for the event - but he was surprised by how relaxed the evening turned out to be.
He tells British talk show host Graham Norton, "I was with The Queen and the President just last week. For an American, I kept trying to figure out, 'Why am I here? How did this happen? Did I win a ticket? Is this Charlie And The Chocolate Factory?'
"We got an email from the White House saying, 'The President and Mrs. Obama would like you to join them for dinner at Buckingham Palace...'
"We got there and it turned out it's a surprisingly informal (event). Everybody says, 'Hello, I'm Julie!' and 'I'm Simon! Nice to see you! How are you?' It's kind of like on a first-name basis.
"I talked (to the Queen) about doing Shakespeare. That was how I got my start in the United States and we compared notes on that. She said, 'We love to go to the theatre!' That was my moment with Her Majesty."