In the scene where the entire gang of people move into the basement to be properly equipped with laser guns, everyone is there, and everyone has a gun. When the camera goes to the cripple in the wheelchair, and then back to the group, someone is missing. The one who is missing is the ditzo in pigtails. Seeing as how they locked the door, there's no way she could have just gotten out. That's right, when they were finishing off the scene, they forgot to put her in. She just... dissappeared!