|Prototype Model Unit XJ-4|
|Age||Unknown (preteen-like in mentality)|
|Likes||The XJ-Sisters, cleaning/making sure everything is clean, fighting against villains|
|Family|| XJ-1 (younger sister)|
XJ-2 (younger sister)
XJ-3 (younger sister)
XJ-5 (older sister)
XJ-6 (older sister)
XJ-7 (older sister)
XJ-8 (older sister)
XJ-9 (older sister)
|Enemies|| Dr. Locus|
|First appearance||Sibling Tsunami|
|Voiced by:||Kath Soucie|
Prototype Model Unit XJ-4 is the fourth sister of Jenny.
Appearance and Personality
XJ-4 has a mostly lavender and white color scheme. While she has only one leg-like appendage, which allows her to move with the help of a wheel, she possesses four long robotic arms. Each arm has two fingers, and these arms aid in her goal to retain neatness, as she can grabbily multitask quite well with them. She has three antennae, two on the left and right of the top of her head, and a longer one in the middle. Her longer antenna has a bow tied to the middle of it.
Built assumingly for cleaning and multitasking, XJ-4 is incredibly devoted to making sure everything is perfectly clean, even to the point of chiding other characters for messes they can't possibly help but create. She has proven to always be there for her sisters, and especially tends to the youngest baby sister XJ-1.
XJ-4 can produce many, perhaps all, types of cleaning utensils and products. Along with this, she can also work with the other XJ Series robots to create various structures and weapons. She sometimes prefers to use cleaning utensils in place of weapons.
- Near the end of the episode Turncoats, while Dr. Wakeman is repairing her and her sisters, XJ-4 asks if she'll have the ability to spray Scrubbing Bubbles. This is a reference to the trademark bathroom cleaner.
- She is the oddball of her sisters in terms of her overall design as XJ-1 to 3 and 5 to 9 follow a similar design scheme: A blue/aquamarine & white color pattern, pigtails, and/or an upper body consisting of a "tank top and a mini-skirt".