"The craziest thing that ever happen to me, was like, [Tumblr blog ] Old Loves is my passion, I check it, like, once a week," she said. "It's how I kick back on a Friday night is to see what Old Loves has done. And I was going through it and I saw my boyfriend and his girlfriend from high school. Scarlett Johansson. I know I shouldn't spill that in a public forum, but you can Google it."

Jack Antonoff, 29, dated Johansnson, who is the same age, for a year when they were 17, while they were attending the Professional Children's School in New York City. Dunham said she had no issue with the fact that the pair used to date.

"I'm not jealous. It's very sweet. I love looking at pictures of them," she said. "She's beautiful, he's beautiful, but it was just so surreal to be looking through this blog that gives me so much pleasure and then there's my boyfriend. And I was like, "My mind is going to explode. I really did think I was hallucinating. It would be like seeing my parents."