FusionFall was a Unity-based MMORPG from Cartoon Network. In the game, Dexter needs you to be under his guidemenship to find all the Lost Heroes, such as the other two Justice Friends.
At the old FusionFall, Dee Dee was the reason you got sent into the horrible universe.You had to sit through a walkthrough animation, and have Dexter take you into the future. Dee Dee comes in with her famous pickup line:"Oooh! Whats this button do?" and you are sent into The Future, where its horribly infected by Planet Fusion.You would meet up with Ben and Numbuh Five and learn how to attack, and then get your first nano: Buttercup.
In 2010, The future has been replaced with the new training areas called "Academic": Mt. Neverest, a play on Never and Everest (and the location of the Justice friends headquarters, at least in the Powerpuff Girls TV series. This is proven further by the fact that statues of Justice Friends, Monkey, Super Cow from the Cow and Chicken TV series, and Billy's alter ego from The grim adventures of Billy and Mandy TV series); Providence HQ, a dangerous zoo full of enemy from Generator Rex; and the Null Void, the area full of fusion spawns where Villains like Vilgax from the Ben 10 Series are held, or use to be. Mt. Neverest is nicknamed Graduation Level, with Providence HQ Petting Zoo and Null Void Training Level.
On August 29, 2013, the game's servers were shut down.
As of July 17, 2017, the game has been revived by a group of fans using an older more "stable" version of the game from 2010. The game has been renamed FusionFall Retro: