(Not to be confused with Jack’s Apartment.)
Jack’s House is a location in Elmo’s Country. It is Jack’s spare house/old residence.
Jack’s house debuted in Elmo’s Country 2, as his original residence. He uses it as his homebase and eventually, he moves to a different place. However, the house returns in Elmo’s Country 4, where Hybrid and Elmo land. Jack also uses it in Elmo’s Country 5.
Jack’s house is simply a middle-class house. There is a living room, a bedroom, a basement which serves as his lab, and a kitchen. The house formerly had a green SUV parked in the driveway, which Elmo crashes by mistake. Jack’s lab is by far the most complex room, complete with chemicals, computers, and a device called the Flaming Tomb, which is a special type of incinerator. There is also a replica of Jack’s brain which is used to power Jackborg. Jackborg himself sits in a corner of the lab.
It is not used that much in the series.
It is the second location introduced into the franchise, the first (obviously) being Elmo’s Country.
It is technically the third if you count Elmo’s Second Factory.