War Against Fuse
Numbuh Four is nowhere to be found in the Future. It's likely that he fell alongside many other heroes.
In the Past, he's at Mount Blackhead with Numbuh Three. He helps the player find and take on Fusion Toiletnator and also hands out missions. During the mission for the Mac Nano, he was much needed help when the player tries to recover Mac's bag from Fuse's monsters only to realize a Gooby Trap was set inside. His Fusion lies within the Dinosaur Pass Infected Zone found within the Darklands. The Fusion Numbuh Four secret lair is outside the Infected Zone near the Really Twisted Forest.
- Fusion Numbuh Four and Fusion Numbuh Three are the only Kids Next Door fusions to not use any equipment of any kind in their boss fights.
- He is voiced by Dee Bradley Baker, who also voices the Toilenator, Swampfire, Humongousaur, Echo Echo, AmpFibian, and Spidermonkey.