The Hurt Locker star found himself at the same party as the Girls actress and struck up a conversation with her in the hopes of asking her out - but his efforts fell flat.
MACkie tells U.S. late night host Seth Meyers, "She shot me down, I stumbled over something (I said to her). I said, 'Wow, you're really pretty,' and she said, 'Thank you,' and she said, 'Well you know I'm doing this show and it's going really well,' and she said, 'What are you working on?' and I said, 'I got some things coming out.'
"It was a slow time... I didn't have anything to talk about and she was like, 'Oh,' and her publicist whisked her away so fast it was like a poof of dust."
Dunham has since started dating fun. rocker Jack Antonoff.