According to White House sources, President Obama took a break from his national security briefing today in order to wait for just the right moment to stroll casually past an unsuspecting group of visitors taking the daily 9:30 a.m. guided tour of 1600 Pennsylvania Ave. 'Man, the look on their faces when they turn the corner and I'm just standing thereit's going to be insane,' the president reportedly said while peering from behind a slightly ajar door in the West Wing and debating whether he should quickly cross behind the guide so the visitors would not even be sure they saw him, or sneak up behind the group and ask a question about White House history as if he were part of the tour. 'I mean, they are totally going to shit their pants when they see me. This is going to be amazing.' Obama added that once he made his introduction, he planned on handing the person at the front of the group his presidential pen and casually joking that he didn't want to see it ending up on eBay. 