As shown in "The Ballad of Duke Baloney!", Mann and Fisher rescued Flintheart Glomgold after he fell into the sea and disappeared for months during the events of "The Shadow War!". However, it turns out that Glomgold is pretending to be "Duke Baloney" the whole time just as she and the other citizens of Duckburg turn against him for his lies.
Role in the series
Mann and her companion Fisher are first seen bringing a net to their ship, looking at something weird they caught during their fishing campaign. They discover an amnesiac Flintheart Glomgold upon capturing him. When Louie and Webby arrive at Bait 'n Such and talk about what happened to Glomgold (disguised as "Duke Baloney"), she and Fisher arrive at the spot where their conversation is interrupted just as Mann tells the two that Bait 'n Such is a bully-free zone as she does not tolerate anyone bullying employees. Just as the two leave, Louie and Webby discuss about Flintheart Glomgold's disappearance in Duckburg. Meanwhile at Chums when Glomgold is talking with Louie and Webby as she and Fisher introduce "Duke" to the two. Trying to prove to reveal Glomgold's true identity, she and Fisherprepare to investigate the case of Glomgold's disguise as she, Fisher, and Glomgold leave Chums and discover the McDuck Enterprises fishing boat arriving back on shore. Glomgold, however, slowly remembers that the boat is linked to Scrooge McDuck as Mann tells him to catch up with the two. Later, Glomgold brings Mann and her companion Fisher to catch more fish than the McDuck Enterprises boat in order to make him rich. Devising a devious scheme towards the two, Fisher warns that if they overfish, the ocean will have less fish than before just as Glomgold ends up joking. Just as she and Fisher leave, Glomgold decides to take revenge against the McDuck Enterprises fishing boat while Louie and Webby are having trouble finding out who "Duke Baloney" really is. The next day, Glomgold arrives where Mann and Fisher greet him where they want him in their family with the sign he received from them. Scrooge McDuck, however, arrives and interrupts the conversation between the couple and Glomgold as he is looking for "Duke Baloney" to which he decides to let his nemesis part of the couple's family. When Louie and Webby are in danger, Mann is seen among the crowd cheering for "Duke" who is about to save them. However, it is found out that "Duke Baloney" is Flintheart Glomgold (due to his disguise beard disintegrated by thunder) the whole time just as Mann and the crowd turn against him for his lies and deception to the citizens of Duckburg.
In "Moonvasion!", Mann appears as a victim under threat of the Moonlander alien invasion. Her further fate is unknown after the battle ended.