Plankton's Death Robot was one of many inventions created by Plankton. It only appeared in the episode "Eek, An Urchin!"
The Death Robot is a rather small robot that moves around on one wheel. It is blue in color and has one eye, just like its creator, Plankton. It also has a red button near the bottom used for its features. It also has two robotic antennae on its head representing Plankton's antennae.
Target Select: This feature tells what the Death Robot should attack. The three pictures shown are a sea horse, Mr. Krabs, and sea urchins.
Mallet: This is the Death Robot's main feature. After its target has been chosen, it will start to chase down that target until it smashes it with the mallet.
Super Strength: The Death Robot uses its arms to rip open anything with ease. This was shown when it tore apart a table and Mr. Krabs' shell.
The Death Robot was destroyed by Mr. Krabs when it attempted to smash the sea urchin while it was inside his cash register. The Death Robot ripped apart Mr. Krabs' shell greatly upsetting him. The robot puts him back together but Mr. Krabs then takes the mallet from it and starts to smash it turning it into a lunchbox.
Oddly, when Mr. Krabs smashed the Death Robot into a lunchbox, the robot was smiling in the picture even though it has no visible mouth.