Shnooky and his unit were sent to Earth to gather information. However, when they saw a bunch of human infants in a hospital, they mistakenly believed that the babies were Nar-Gh'ok hostages. Shnooky's team then "liberated" the infants by teleporting them to their ship, but when the unit was discovered by hospital workers they were forced to take the place of the babies they freed and have been stuck on Earth ever since.
In the seven years that followed, Shnooky was forced to pose as "Noogums", a normal human infant. However, Shnooky was caught spying on Zim when the Irken saw him looking through a window at him landing the Voot Cruiser. Zim then went to Noogums's house, posing as a Neighborhood Baby Inspector with the hope of interrogating the witness. However, this attempt failed when Zim was driven away by a foul stench secreted by "Noogums".
Later that night, Shnooky and his infantile comrades invaded Zim's house and took him prisoner. Their goal was initially to simply steal the Voot and get home, but after all the trouble Zim had caused them, Shnooky and the Nar-Gh'ok merged to form "Giganto-baby", and laid waste to the Irken's base. Fortunately, a power amplifier was on hand, and with the help of GIR, Zim managed to hit the Giganto-baby with paralysing waves of stupidity, separating the colossus and lowering the intelligence of the Nar-Gh'ok warriors to that back to that of normal babies.
Shnooky was then catapulted back into his crib by Zim, and never makes an appearance again.