Balloon rocket

Besides being simple toys, balloon rockets are a widely used as a teaching device to demonstrate basic physics.

If the balloon is inflated with helium or other lighter than air gases, it tends to fly in an inclined trajectory (usually going upwards), due to the light nature of the gas.

The balloon rocket can be used easily to demonstrate simple physics, namely Newton’s third law of motion.

[3] There is also dedicated toy known as a rocket balloon, usually tubular-shaped and inflated with a special pump (pictured).

For instance, when an object or a character is comically being "inflated" and then deflates, it flies away uncontrollably, in a similar fashion to a balloon itself.