XJ-4 is an octopus-like robot who is a neat-freak. She has a neatly-square head with several tentacle-like arms underneath and a straight, upward ponytail with one rather-large bow. The head is situated on a stalk with a wheel on the end. Instead of weaponry, she has various cleaning gadgets (like a dust pan, a mop, a broom, and, rather obviously, a vacuum cleaner). She seems to be based on the idea/stereotype that many future robots will be domestic helpers, and possibly to be able to clean up the aftermath of a battle. All XJ robots starting from her have the ability to speak understandable English. She was designed in early childhood. In SpongeBob and Nicktoons: the Series, XJ-4 is now SpongeBob's sweetheart.