The XJ-Sisters make their first appearances in the Season 1 episode, "Sibling Tsunami", and go on to appear in "Sister Sledgehammer", "Agent 00' Sheldon" and "Escape from Cluster Prime" (mostly cameo), and notably "Turncoats." (XJ-8 also appears briefly in "There's No Place Like Home School").
In "A Robot For All Seasons," Nora Wakeman was seen designing plans for an XJ-10 after Jenny was believed to have gone renegade due to falling under the control of Todd Sweeney. However, XJ-10 was never actually created.
List of XJ-Sister Robots
- Nora Wakeman presumably started building the XJ-Sisters to replace Armaggedroid in order to create a new robotic Earth defender due to him going rogue.
- In the Russian version of Season 3, XJ-4, XJ-6, XJ-7, and XJ-8 were all voiced by a male actor.