In FusionFall, Buttercup originally appeared in The Future as one of the few remaining heroes, with Samurai Jack, Dexter, Numbuh Two, and Numbuh Five, to have survived the battle in Tech Square to give the player missions. None of the other characters appeared in the Future, revealing that Buttercup was the onlyone of her sisters to survive. She seems to have completely recovered from her memory loss, but oddly doesn't mention Ace at all. She does, however, mention that she had lost her memory and joined a band, but has now recovered. She was also the first Nano as well as the first Blastons Nano that the player created, until the introduction of the Academy.She originally could be found in front of the Mall in Pokey Oaks North near Numbuh Five in The Future. Returning to the past, Professor Utonium mentions Buttercup had a battle with Mojo Jojo over the ocean and was said to have never been seen again. She can be found in the Downtown section if the player performs the first part of the Music and Mayhem mission, in which Mandark needs Buttercup's leather jacket for Nano improvement, or if you are performing the Ms. Missing guide mission from Dexter. Apparently, Buttercup had amnesia but eventually regained her memory after her battle with Mojo. During this time, Ace takes her into his band under the identity of Belladonna.
She can give out the "I'm Still Standing" mission, in which the player tells Buttercup's family about her whereabouts (in order of Professor Utonium, Blossom, and Bubbles) and participates for a few parts of the "How to Date a Fusion" mission, in which the player eventually faces Fusion Buttercup again. Buttercup also gives the mission "Drop Your Weapons (Part 2 of 5)," after she contacts players during the first mission for Coco, while Mandy contacts players when they are done with Part 2.
She informs the player that Ace, the leader of the Gangreen Gang, had taken her into his band. She also mentions that Ace is her boyfriend (a possible reference to The Powerpuff Girls episode "Buttercrush"), as proven in the Valentine's Day event and the mission "How to Date a Fusion."
- Like her sisters, Buttercup was designed with more human features such as ears, a nose and fingers (features she didn't have in the series).
- Hers was the first original Nano, as well as the first Blastons Nano, received before the Academy was added.
- In both the future and the past, Buttercup can be seen (along with Bubbles) wearing a white utility belt. This could be a reference to the show PowerPuff Girls Z, as there they also wear white utility belts.
- Buttercup is one of the few remaining heroes that survived the Fall of Tech Square in the Future.
- Even though Buttercup is dressed in her 'Belladonna' attire in the past, her text box still uses the name "Buttercup". Additionally, Fusion Buttercup's attire and hair style is based on Buttercup's 'Powerpuff Girl' design, and keeps this appearance for both the Past and the Future.