Start up the 'Streets of New Mombasa' level, at any difficulty, so you're at the very beginning of the game and proceed through the level like normal. After activating the Superintendent, you will be instructed to enter the first building in the game and will come to a courtyard full of grunts. Before you enter the courtyard, look to your right and you will see a couch in the corner and a box of cereal laying in front of it. Walk up to the box and it should pop. If it doesn't, try zooming in and out on it repeatedly until it does.