ZIM receives a top-notch Irken weapon by mistake and tries to use it to destroy Dib once and for all / All the children in the Skool are infested with lice, and, ironically, only ZIM can help them.
The Tallest send a specially-weaponized walking suit to one of their loyal minions, and a load of malfunctioning SIR units to ZIM (hoping they'll help destroy him). However, a disgruntled Postal employee switches the delivery tags. The loyal minion's plan id destroyed, and ZIM is overcome with joy at receiving the walking suit, called 'The Megadoomer.'
Zim intends to use the suit to destroy Dib, but soon finds out that the suit contains no batteries. using a plug-in adapter to power it up, Zim is totally oblivious to the fact that the suit's cloaking device cloaks the suit...but not Zim or the power cord attached to it!
Upon arriving at Dib's, the suit's power supply fails, and Dib starts taking pictures. Panicking, Zim sets the suit to self-destruct. In the aftermath, Zim claims that this was all a plan to steal Dib's camera. Dib steals the camera back and claims victory...only for Zim to tell Dib that the lens cap was on...and there's no pics of the Megadoomer. Zim declares victory once again...only to be hit by a flying piece of debris from the exploded suit.
Back on their ship, The Tallest receive word that the Megadoomer exploded. Their thoughts turn to the possibility that Zim may finally have been annihilated...but they soon figure they're not that lucky.