Formerly a cleaning lady at a research lab, an accident with an experimental disinfectant in the lab spread fumes all throughout the place, which she accidentally inhaled. This incident twisted her mind, turning her into a insane clean-obssessed person.
She eventually joined FOWL, committing crimes with as much soap as she can. Darkwing Duck even describes her as "Mrs. Hyde". She leaves everything immaculately clean and is deathly afraid of dirt. She has a sister called Ample Grime, which is the polar opposite of her, loving dirt as much as Ammonia loves cleanliness. Strangely, however, Ammonia is quite protective over her little sister, who also happens to be a FOWL agent.
Crisis on Infinite Darkwings
Ammonia had stolen a great amount of cleaning supplies to build an air freshner bomb and was being pursued by the police. She was able to escape when the police were shot out by the mind-controlled Quiverwing Duck.
Ammonia had been guarding F.O.W.L.'s inner sanctum along with Hotshot and Flygirl when they were run into by Quiverwing Quack and Arrow Kid. Quiverwing and Ammonia fought while Hotshot and Flygirl chased after Arrow Kid. When Quiverwing and Arrow Kid were distracted by the sight of Hotshot and Flygirl crushed by an anvil, Ammonia shoved them into buckets, saying if they tried to escape, they'd be destroyed by nanotechnology in the buckets. Femme Appeal saw Ammonia with the kids and decided to blow her cover to save them, while revealing that Ammonia was all for reviving Duckthulu, believing his presence would rid the world of dirt. Appeal was able to free Quiverwing and A.K., only for them to be captured once again. Appeal was still able to fight back against Ammonia, but while they were distracted by Arrow Kid's mutation caused by the rising presence of Duckthulu, Ammonia tried to attack once more, only to be turned to mud by Morgana, much to Pine's horror.
Ammonia returned, changed back to normal presumably by Magica, as a member of Magica's League of Eve-il. She ended up joining the slime with Negaduck and the other villains and was sucked into the wasteland dimension with them when Darkwing hit Negaduck with the truth.