Schematic: Mechanical Squirrel Box

Schematic: Mechanical Squirrel Box is a schematic; a recipe used in Engineering. It can be used to learn how to create a Mechanical Squirrel Box which then can be used to obtain the companion with the same name - a Mechanical Squirrel.

Source
This is a world drop, mostly dropping from mobs in a level range from 5 to 20. It can also be fished in areas with this range. Naturally, it can also often be found on the Auction House.