Watt became trapped in a lantern by the Big Lantern Ghost, but Mario defeated him and he ran off. Mario then broke the lantern with his hammer, setting Watt free, and she joined Mario's team. Together they defeated General Guy and his army of Shy Guys and rescued the fourth Star Spirit, Muskular.
Together they traveled through more areas until they rescued all seven Star Spirits and defeated Bowser. Afterward, Watt returned to Shy Guy's Toybox, where it is hinted that the Shy Guys are no longer evil. She also received an invitation to a party at Peach's castle.
Outside battle, Watt can illuminate dark areas. This will only happen if Mario is using Watt's ability, and the area will get dark again if he turns off the ability or switches partners. This can not only illuminate dark areas, but reveal hidden blocks as well.
In battle, Watt's techniques are:
- Though Watt is stated to be female in Paper Mario, her catch card in Super Paper Mario seems to think she is male, saying "This guy was pretty bright for his age!"