The chum detonator was an explosive that appeared in the episode "Jailbreak!" It was invented by Plankton, although the soap part of it was carved by the whale cellmate.
The chum detonator appears to be a combination of Plankton's chum and a simple bar of soap. It also has wires going through it. The chum acts as explosive material, while the soap acts as a timer device to initialize the explosion.
Role in episode
The chum detonator was used by Plankton to blow apart a wall in the Bikini Bottom Jail. It was successful, but the prison guards cover up the large hole with their bodies. However, they get stuck in place and Plankton and his cellmates go out through the front door.