A chick can spear the roof of a Bus?
A 15 yo chick can run a spear through the roof of a Bus?
What is the bus made of? Tinfoil?
The roof of the bus is probably thin aluminum braced with a ribcage frame. Those dudes sunbathing on top could probably cause dents if they stood upright and jumped a bit.
A spear with enough weight is designed to focus momentum of a sharp point. A healthy upperclass cheerleader in fear of her life should be able to get it done.
Have you ever opened a can of juice with a punch-type can opener? That's pretty strong too, but you've got multiplying leverage focused on the very point of the opener.
Plus movie magic.