9-Volt's bedroom is the most frequently seen room, being the only one to appear up until Game & Wario. Since 9-Volt loves video games, his bedroom is scattered with video game consoles from the past and present. In WarioWare: Twisted!, 9-Volt invites 18-Volt to his house to play his NES.
The house is the main setting of the Game & Wario minigame Gamer, hosted by 9-Volt & 18-Volt. 9-Volt's mode takes place inside his bedroom, while the house can be seen across the street during 18-Volt's mode.
The house reappears during 5-Volt's stage in WarioWare Gold, in which 5-Volt watches Mr. Sparkles' bodybuilding exercise on their television.
In WarioWare: Get It Together!, 9-Volt and his Fronk pet play his Epic Augmented Reality Game past his bedtime in his room without 5-Volt knowing. Additionally, the intro cutscene for the Anything Goes level has the exterior of Wario's House briefly turn into 9-Volt's due to the Mega Bug's corruption and the house also appears during the cast credits for this game, in the background when 9-Volt, 18-Volt, 5-Volt, and 13-Amp are credited.