[1] The game took place within an amalgamation of Cartoon Network settings that included characters and locations from established shows as well as some unique additions, following a science fiction genre.

On April 16, 2020, Cartoon Network issued a DMCA takedown notice to the developers of the games, resulting in Retro being removed entirely and Legacy's cancellation.

[6][7] The game world features over 50 characters and several areas based on current and past shows on Cartoon Network.

[8] Uncommon in MMORPG's of its time was the platforming gameplay significantly present in FusionFall, with Community Director Rich Weil emphasizing the developers' intent to make the game "as three-dimensional as possible".

By defeating enemies, players progress towards leveling up and receive currency, called taros,[10] to buy clothing and weapon upgrades.

[2] Playing past level 5 originally required a monthly paid subscription in the form of redeemable cards that could be purchased at participating retailers.

[18] Four periods of open beta testing took place between November 14, 2008 and January 11, 2009, available to anyone with an account on Cartoon Network's website.

[citation needed] When it was first released, FusionFall required a paid subscription for the full game, with a limited portion of the content available for free.

[1] The Victory Packs were eventually discontinued, having been replaced with one-month and three-month game card available for purchase at Target outlets.

[25][26] In the year of its release, FusionFall received coverage from such news outlets for technology and gaming as Ars Technica,[13] IGN,[33] Wired,[2] Engadget,[34] and the Unity engine blog[35] among others.

Playable characters include Finn the Human, Fionna the Human, and Marceline of Adventure Time, Dexter of Dexter's Laboratory, Mordecai and Rigby of Regular Show, Four Arms and Feedback of Ben 10, Gumball Watterson of The Amazing World of Gumball, Mojo Jojo of The Powerpuff Girls, and Johnny Bravo of his eponymous show.