Fawful accompanies Cackletta, disguised as The Goodwill Ambassador from the Beanbean Kingdom, to the Mushroom Kingdom during the events of the game, where he aids her in stealing Princess Peach's voice, which was needed to awaken the Beanstar. While the two are on their way to the Beanbean Kingdom, their kingdom of residence, they encounter Mario, Luigi, SMG4, and Bowser, who have formed an alliance to stop the two villains. After taking care of Bowser, Fawful attacks the Mario Bros. as well as SMG4 who manage to destroy his Vacuum Helmet. However, Fawful summons another Vacuum Helmet after that and uses it to knock Bowser's Koopa Cruiser out of the sky before departing. He is later hinted by Beanbean guards to have kidnapped Prince Peasley, after they wrongly accused Mario, Luigi, and SMG4 of doing so. He is not seen again until the trio arrives at Hoohoo Mountain, where he blocks their path with a large stone. He later appears in Beanbean Castle, stealing the Beanstar alongside Cackletta and force-feeding Queen Bean, the kingdom's benevolent ruler, a Belly Blech worm to aid in their escape.
The villainous pair next assaults Woohoo Hooniversity, where he and Cackletta plan to awaken the Beanstar using several Peach-bots, which Fawful had designed. However, due to some planning on the princess's part, the voice used is that of Birdo, which irritates the Beanstar so much that it smashes through the floor and into the basement. Shortly afterward, Mario, Luigi, and SMG4 arrive, and before he can do anything, Luigi knocks him into the ground. After dispatching him, they incapacitate Cackletta. Fawful soon recovers and sucks his mistress's energy into his Vacuum Helmet. Before he can attack the trio again, he is sent flying through the roof by Prince Peasley. Landing in Stardust Fields, Fawful finds an unconscious Bowser, whose body Cackletta possesses. Cackletta then begins to call herself Bowletta. Fawful then accompanies her to Little Fungitown, where they abduct the princess. Mario, Luigi, and SMG4. later encounter Fawful at Joke's End under the pretense of exchanging the Beanstar for Peach, though they use a fake. Fawful recognizes this, however, and takes the real one as well as Princess Peach on board a repaired Koopa Cruiser. However, this Princess Peach is actually Luigi in disguise, who utilizes the pair's rage and shock to retrieve the Beanstar and escape. Fawful then follows Cackletta to Bowser's Castle, from which she plans to destroy both the Mushroom and Beanbean Kingdoms.
Fawful is encountered in the castle as the penultimate boss, clad in a pink outfit with wing-like cloth under his arms and a large V-neck. He can now attack with a large mechanism that resembles his head. After his defeat, he begins a final attack in desperation, entering a banter-fest with Prince Peasley, but is knocked out of the castle and explodes before Mario, Luigi, and SMG4 engage his mistress and her soul, the latter of which conjures an apparition of Fawful as one of its attacks. This apparition of Fawful attacks similarly to how he does in his first battle.
This is Fawful's only appearance in an actual Longplay. His voice can be heard in a few others.