Happy Volts caters to the mentally ill residents of Bullworth, as stated by its sign ("Home for the Mentally Unwell") which may include the Townies Otto Tyler, Leon and Clint (aka Henry), who Jimmy helps return to the asylum. During the course of the game, the English teacher Mr. Galloway, and Greaser leader Johnny Vincent are admitted into the asylum, only to escape with help from Jimmy. And during the missions, Fenwick can also be seen on grounds. It is also rumored that Gary Smith was admitted into the asylum.

The building is divided into three blocks A, B, and C, Block B being reserved for patients who have violent tendencies. At first glance it may seem that only A and B block can be accessed, as only those two have the icon indicating that the door can be opened. However, the door to C Block can be broken down through punches, jumping against it, or weapons. Blocks A and B are in active use, but C Block is run down and decrepit. There is a mortuary located inside C block, along with what appears to be operating tables and a X-ray viewer depicting x-rays of humans with physical defects. If Jimmy regularly visits Block C he may encounter a door marked with EMPLOYEES ONLY with a green arrow under it, which is normally locked. If Jimmy opens this door, he will enter a fenced-off area. He will not be able to return to the building, and will have to wait till 2 am. Alternatively, Jimmy can use a weapon to hit an orderly though the fence, then he will be busted through the wall and then brought to Blue Skies Industrial Park police station. (Jimmy must be close up to the fence otherwise the orderlies won't spot him.)

During free roam, not a single patient is seen in the cells, though they can be heard screaming. The asylum is patrolled by the Orderlies, who wear white uniforms and look for trespassers. This interior is the most interactable in the entire game. If Jimmy wears the Black Ninja Outfit or Orderly Uniform he can explore the asylum without getting in trouble for trespassing.