Miscellaneous Planets

Planet Name: Planet of Broken Glass, Exploding Head Planets

Mentioned in: Germs

Inhabitants: Unknown

When Zim bothers the Almighty Tallest with another mission report, the Tallest contemplate other potential places they could have sent Zim:

Purple: Zim. You know we really should've given him a mission on a sun or a planet of broken glass or something.

Red: Or one of those exploding head planets.

Whether or not such planets actually exist is unknown.

Planet Name: Sirus Minor

Mentioned in: Door to Door

Inhabitants: Unknown

Zim mentioned this planet prior to his heat-induced hallucinating:

Zim: So hot! Even Sirus Minor didn't orbit such a miserable star!

From that statement we can assess that Sirus Minor is planet well-known for being a hot place.