In 2004, Psy allegedly rapped the following:
The lyrics and English translation — which we're told by a Korean speaker is correct — were posted as a CNN iReport two months ago and picked up recently by Twitchy and Mediaite. His appearance at the concert is apparently well documented in Korean media.
The song was originally done by the band N.EX.T:
It's still not clear if Psy actually helped cover the song. But he does have a history of appearing at protest concerts. Anti-American sentiment began mounting in South Korea in 2002, when American soldiers struck two South Korean schoolgirls during a training exercise.
The Korea Daily blog has photos of Psy from some of these shows in the early 2000s:
Outrage toward the Korean pop star is slowly spreading. On Friday, a petition was posted to the White House's We the People page, urging President Obama to rescind Psy's invitation to perform at a Christmas party. (Psy has not been invited to perform at the White House, but rather the annual Christmas in Washington party, held at the National Building Museum.)
Update: In a statement Psy apologizes.
"As a proud South Korean who was educated in the United States and lived there for a very significant part of my life, I understand the sacrifices American servicemen and women have made to protect freedom and democracy in my country and around the world. The song in question — from eight years ago — was part of a deeply emotional reaction to the war in Iraq and the killing of two innocent Korean civilians that was part of the overall antiwar sentiment shared by others around the world at that time," the statement read. "While I'm grateful for the freedom to express one's self I've learned there are limits to what language is appropriate and I'm deeply sorry for how these lyrics could be interpreted. I will forever be sorry for any pain I have caused anyone by those words.
"I have been honored to perform in front of American soldiers in recent months — including an appearance on the Jay Leno show specifically for them — and I hope they and all Americans can accept my apology," the statement concluded. "While it's important we express our opinions, I deeply regret the inflammatory and inappropriate language I used to do so. In my music I try to give people a release, a reason to smile. I have learned that though music, our universal language we can all come together as a culture of humanity and I hope that you will accept my apology."