Lighteegee was a Fakegee who radiated light. In fact, in his picture, you can see uneven patches of light streaming off him.
One day, Lighteegee was flying around the United 'Gees Galaxy, when Ultimate Treegee's laser came out of nowhere and hit him. Treegee had been practicing his Ultimate Treegee powers, and had lost control of his laser. The laser smashed Lighteegee into a planet, killing him from a combination of the collision, the laser, and the radiation.
Grimeegee saw this as a perfect opportunity. Terrifiregee and all that Fakegees he had created (except Peacegee) hated Lighteegee for all his light, so Grimeegee brought him back to life. However, he changed a lot: Lighteegee was now evil, and his new name was Darkeegee.