When Zim learns the Irkens are planning a new invasion called Operation Impending Doom II, he, not understanding the purpose of his exile, "quits being banished" and leaves Foodcourtia and travels to the convention center planet called Conventia, for the Great Assigning, an event where Irken Elite soldiers are chosen to become Invaders and are then assigned by The Tallest to a planet. Invaders are soldiers whose missions are to blend in with the indigenous life forms of their assigned planet, collect information about the planet and its inhabitants and prepare the planet for conquest by the Irken Armada. Zim is determined to regain his status as an Invader and pleads with The Tallest to assign him a planet. In a desperate act to get Zim as far away as possible and ensure he would not ruin things the second time around, The Tallest send Zim on a fake "secret mission" to a "mystery planet" located on the outskirts of their known universe which they do not think even exists, in order to keep him occupied and away from the real invasion. Zim is joined in his mission by GIR (Rosearik Rikki Simons), an ineffective and erratic Standard Issue Information Retrieval (SIR) unit which was hastily made out of spare parts found in a trash can.