Invader Larb is a very lucky Irken. He was originally assigned to Blorch, home of the Slaughtering Rat People. When he came before the Tallest, though, they recognized him for his increased height and re-assigned him to planet Vort, home of the universe's most comfortable couch.
Sometime during the course of the series Larb successfully conquered Vort, as we see in Backseat Drivers from Beyond the Stars.
Invader Skoodge is short, fat and ugly. These traits do little to endear him to his leaders, The Almighty Tallest, and in fact they try to get rid of him several times...