That is an HID bulb, you'll find a small box (transformer) near it. Most do plug into the stock harness, because all H7 plugs are the same.
OH! I get your confusion now. Lol.
You are jamming the stock bulb into the wrong side of the connector. The Yellow and Black wires are stock and the back side of the connector. Unplug the Red and Black wires from the other (front) side. They are going to the aftermarket ballast, and thats where your standard bulb plugs in once you disconnect those wires.