Penn took to the stage at a gallery in New York over the weekend to show off a few skills he learned playing Jeff Buckley in the recently-wrapped biopic Greetings from Tim Buckley.
Singing 'Lilac Wine', a song written in 1950 by composer James Shelton and covered by Buckley on his '94 album Grace, Penn shrugged off sceptics who reckon he's not suited to play the musician.
In fact, he gave a damn impressive performance and we're not the only ones who think so.
The blogger who filmed Penn's stage debut wrote, "His vocals reminded me so much of Jeff Buckley. His guitar playing was a little similar, too. I was in awe with this guy's vocals. It was something very unexpected."
Check out the clip above and have your say by voting below: do you think Mr Gossip Girl does the great Jeff Buckley proud?