The Brain Gain Machine is a machine that is used by Numberjacks to solve problems. It's located in the Control Room.
The Brain Gain Machine is a purple machine with six pillars containing a green liquid-like substance, called "brain gain". On the top is a blue six-legged spider-like figure with wires attached to the ceiling.
When the machine is turned on, the walls turn from opaque to transparent, and the center platform lowers to the ground for a Numberjack to get in the machine. The six-legged figure flickers, bounces, and raises one of each of its legs at one time. Then it rolls its "arms" and sucks up the brain gain liquid into itself, and the pillars now contain purple "electricity" inside.
When a Numberjack hops onto the center platform, the electricity from the machine bolts out of the house and into a Numberjack on a mission to sort the problems.
Sometimes a Numberjack can cause a mistake in the machine or overflow with brain gain, which causes more problems in the real world.
"1, 2, 3, Go" is the only episode where the Brain Gain Machine is not used.