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“9-Volt!! It's past your bedtime!”
5-Volt is 9-Volt's mother and makes a few appearances in the WarioWare series. She is never fully seen until Game & Wario. 5-Volt lives along with 9-Volt and presumably his pet Fronk in a house in Diamond City.
5-Volt (though not named such) is first mentioned in the diary section of the WarioWare, Inc.: Mega Microgame$! Japanese website. In his diary, 9-Volt writes that Wario gave his mother a Game Boy Advance SP for her birthday, which pleased her as she is an avid gamer. According to the entry, 5-Volt's birthday is on March 13. 
5-Volt makes her first ingame appearance in WarioWare: Twisted!, where she shouts at 9-Volt to go to bed since he is playing with 18-Volt all day. 5-Volt is seen only from behind and from the knees down. After 9-Volt has gone to bed, he still furtively plays with his Game Boy Advance SP under the bedspread, but she catches him when she opens his room's door a second time. 5-Volt's silhouette is seen in the doorway.
5-Volt is seen again in Game & Wario, during the Gamer stage. This is the first game to show her face completely. She often drops by 9-Volt's room to check if he is sleeping, and the player must pause 9-Volt's console while she looks at him. She also can attempt fake-outs, as well as be seen on screen twice at the same time. In the cutscene before the game, she appears to take the game 9-Volt and 18-Volt are playing and orders them to do their homework. Once they finish she returns the game to them. They both find out, in surprise, that 5-Volt has beaten their high score.
5-Volt appears as a stage hazard in the Gamer stage of Super Smash Bros. for Wii U, appearing from the bedroom door, the window, or the television, just like in Game & Wario. Also, if there is a sketchbook or a game console on the stage, she can also appear from there. Before she comes, there is a subtle audio cue. There are also fake-outs in the stage including a cat, an old man wearing a wig, an empty door, 5-Volt turning upside down (at the window), or a TV channel with a hand making a gesture. Additionally, 5-Volt may double check the area by entering through the door multiple times or, when at the window, backing up and rechecking. Finally, with a different audio cue, 5-Volt may exit the TV and scan the entire table from right-to-left and back. If players are within 5-Volt's sight when she appears, they will be knocked away as if they were hit by a strong attack. Players can avoid 5-Volt by avoiding her light, using the stage elements as cover.
Official profiles and statistics
Game & Wario character card
-9-Volt's mom (age unknown)
Super Smash Bros. for Wii U Trophy
Names in other languages