XR originally had a very absent personality and was only programmed to learn from Buzz. On his first mission with Buzz, to try to protect the LGMs' Unimind from Zurg, he was destroyed by Warp Darkmatter. He was rebuilt by the LGMs, but since Zurg captured the Unimind, the LGMs' ability to rebuild him was inhibited, resulting in XR being rebuilt with a very human personality.
XR considers Commander Nebula to be his father because Commander Nebula unknowingly signed the papers to authorize XR's construction. XR constantly calls Commander Nebula "Dad", which annoys Nebula considerably.
XR has an "older brother" named XL, who was a failed forerunner model to XR. XL escaped Star Command and rebuilt himself using stolen parts and was a reoccurring villain throughout the series. XL, towards the end of the series, returned from evil and became good by turning on NOS-4-A2, the energy vampire. He was then employed at Star Command where he became an office managing robot.
XR has a taste for the high life. As a result he enjoys money, partying, dancing, beautiful women, and anything luxurious.