Guzelian is a humanoid alien from another galaxy.
Guzelian is a Heed, a species of alien with the intent on conquering the galaxy. His plan was to use a giant holographic projection of a floating head to persuade the Galactic Alliance and Planet Z that he was a Super Being and that the time for peace has come.
Once he convinced nearly everyone to change for peaceful ways, he and his kind waited for the galaxy to dismantle their strongest weapons and defenses. He planned to lead an attack on Capital Planet, followed by Planet Z, after the LGMs and Grubs respectively dismantle Star Command's strongest weapon, the Ultra Spire, and Emperor Zurg's strongest weapon, the Hyper Death Ray, so that their will be no one left to stop them.
He was tricked into revealing his plan to the galaxy by Buzz Lightyear, who was working with Evil Emperor Zurg to stop Guzelian.