At the end of the first episode cliffhanger, Batman and Robin are trapped in The Penguin's vacuum tank, which is filled with helium balloons. As the air is sucked out of the room, the balloons pop.

My weird question is: How did they get those balloons to pop. I'm guessing pea shooters with pebbles, but I don't know.

For some reason, I need to know how they did this, so if anyone knows, please answer.:D