The Sponge Block is the main ammunition of the Ghostbusters Pop Gun. It was the second ammunition to be introduced in a Nerf-like blaster. It is like a mini version of a sponge though it is made of foam. These blocks had very poor range and were only featured in the Ghostbusters Pop Gun. It is possible to make home-made Sponge Blocks. Despite being called as a Ghostbusters product, it has nothing to do with the movie at all.