In the episode "Fine Finny Fiends," Batman and Robin are trapped in a vacuum tank filled with colorful helium balloons.

As the air is sucked out of the room, the balloons pop.

My question is: How did they get the balloons to pop? I'm sure off-camera, they had some crew people sticking them with pins, but on camera, they simply explode.

My guess is they used pea-shooters or something. I know this is an absurd question, but I have to know.:confused: