When a corporate executive attends rock concerts they often have to change out of their button down shirts and slacks and dress in skater/punk/alternative apparel. This is known as their "alternative ego". Derived from the phrase "alter-ego". See Alternative Rock.
When Green Day played down by Wall street, I went to the show dressed business casual because I didn't have my Alterna-ego clothes. I lost a couple of buttons in the mosh pit.