Fawful is Cackletta's servant. He used his Vacuum Helmet to suck out Princess Peach's voice for Cackletta (although both were unaware that it was a Birdo disguised as Peach). When Mario, Luigi, and Bowser set out to stop Cackletta, she sent Fawful after them. Fawful injured Bowser with an energy ball, and he gave Mario and Luigi tips for defeating him. After losing the battle, Fawful shot down the Koopa Cruiser, which crashed in Stardust Fields.
Fawful then kidnapped Prince Peasley, and he and Cackletta turned him into Dragohoho and sealed him in an egg, but he was returned to normal by Mario and Luigi, who then got hammers to get by the block he placed in their way to the Beanbean Castle Town.
Mario and Luigi finally tracked Cackletta and Fawful down at Woohoo Hooniversity. Before Fawful could fight them, Luigi pounded him into the ground, and he and Mario defeated Cackletta, mortally wounding her, so Fawful sucked her soul into his vacuum helmet. At her command he tried to attack Mario and Luigi again, but Prince Peasley knocked him down, beat him up, and slashed him with his sword, sending him flying out of the building.
He later found Bowser lying unconscious, and implanted Cackletta's soul inside him, causing her to possess him as Bowletta.
Fawful waited for the Mario Bros. to bring him the Beanstar at Joke's End. They tried to trick him with a fake, but he wasn't fooled and took the real Beanstar; however, he and Bowletta were fooled when Luigi disguised himself as Peach and said that the Peach that Bowletta kidnapped was an impostor. When they took him aboard the Koopa Cruiser and discovered his true identity, they chased after him, but were cut off, and by the time they reached him, he had escaped with the Beanstar.
Cackletta and Fawful went to Bowser's Castle and flew it to invade the Beanbean Kingdom. After the Mario Bros. defeated the Koopalings, they fought Fawful, and eventually defeated him. Fawful attacked them with his electric antenna, but Prince Peasley knocked him down again. However, Fawful electrified him as well, but Mario pounded him into the ground, and when he got out, Luigi bashed him with his hammer, sending him flying out of the castle where he seemingly exploded.
Fawful was presumed dead; what appeared to be his ghost even appeared in the final battle with Cackletta, however, this was just an apparition created by her, as the sequels confirmed his survival.
The first time he is fought, Fawful shoots energy balls at the Mario Bros. that must be jumped over. He says "Fink-rat!" in red or green letters to indicate who he is attacking. He is not hard to defeat at all, and has 30 HP.
The second time he is fought, he is harder than Bowletta. He starts the battle inside a dome, and shoots lasers, which must be jumped over the instant they flash (as they will then move to attack). Mario and Luigi must keep attacking the dome, until Fawful sends several energy balls spinning around it. Hammering them will destroy them and leave less to jump over once they are far enough from the dome to attack. Fawful's dome will be overheated and shut down for a few turns, allowing Mario and Luigi to attack him. He will also dive at the Mario Bros. several times (raising his hand to indicate who he will attack). This can be countered by hitting his head with a hammer. He can also try to prevent them from dodging his attacks by creating blocks above them that Mario and Luigi must jump into a few times to destroy so they can dodge it.
Fawful appeared not as an enemy, but as the owner of a badge shop only accessible by the babies. In the sewers of Peach's Castle, Baby Mario and Baby Luigi entered a pipe using their mole technique to move underground, and reached Fawful's shop. Fawful told them the story about his defeat at the hands of Mario and Luigi, and how the colors red and green enraged him, but did not recognize them as the Mario Bros., and, while wearing an Elvis costume, traded rare badges for beans. This is the use of beans in this game. Fawful did hint that he would try another attack, however, and that "No baby's candy would have safety".
Fawful returns as the main antagonist. By selling strange mushrooms to Toads, he caused a disease called the Blorbs to make them round and unable to move. He also gave Bowser a Vacuum Shroom to make him (with no memory of this afterward) inhale Mario, Luigi, Peach, and several others, so that they could not join forces with Bowser again as they had previously (such as when they were going after Cackletta). Fawful and his henchman Midbus then began taking over Bowser's castle. Those of Bowser's minions that did not defect over to him were locked up in cages.
Fawful has a number of monsters working for him that greatly resemble him in appearance and name.
When Bowser arrived at his castle, now Fawful Theater, Fawful put the next part of his plan into motion: A caged match between Bowser and Midbus, which he intended Bowser to win, after which he took Bowser to eat food until he got fat and was stuck in the floor. With Bowser completely trapped, Fawful extracted Peach from him with a device so he could use her to awaken the Dark Star. Comically, it was Fawful who had to carry Peach (who was too heavy for him) away, while Midbus, clearly stronger than Fawful, refused to help him.
Fawful stole the Dark Star and began sucking energy from Peach to awaken it. Soon, Bowser attacked him, so he transformed Midbus into Blizzard Midbus and sent him after Bowser, but Bowser defeated him. Fawful began absorbing the Dark Star's power and was transformed into Dark Fawful, but Bowser punched him away before he could finish. Dark Fawful turned Peach's Castle into an evil robot and sent him after Bowser, but Bowser defeated him, returning him to a harmless castle. Bowser then fought Dark Fawful and defeated him (the Mario Bros. destroying his vacuum helmet in the process from inside Bowser), destroying his body but leaving him alive, as a Dark Fawful bug, unable to die while the Dark Star lived.
The Dark Star, in the form of Dark Bowser, absorbed Dark Fawful to become complete. Inside him, Dark Fawful combined with the Dark Star Core and healed him from within whenever Bowser had his HP down to zero. Bowser attacked him to make him cough up Dark Fawful and the core, which Bowser then inhaled for the Mario Bros. to fight. In the end, Dark Fawful and the Dark Star Core were defeated, allowing Bowser to completely destroy Dark Bowser and restore peace to Mushroom Kingdom - a peace that he intended to interrupt by kidnapping Peach. However, Fawful returned, as a head, and near death. He faked remorse so the Mario Bros. would let their guards down, and then selfdestructed in a massive purple explosion in a final attempt to destroy the Mario Bros. Ironically, this only forced them and everyone else out of Bowser, his final ploy failing at the last, and his reign forever brought to an end.
Fawful reappears in the recently released Mario and Luigi Superstar Saga + Bowser's Minions alive and well with almost the exact same role as in Mario and Luigi Superstar Saga but he appears as the main antagonist of Minion Quest: The Search for Bowser where he is seen brainwashing some of Bowser's Minions in order to turn them against Bowser's unbrainwashed minions who are all on the move to save Bowser.
Fawful speaks in Engrish, or broken English, using phrases such as "I have fury" or "I have chortles". He also uses food metaphors, the most popular being "Mustard of Doom" (which is also the name of a Sammer Guy in Super Paper Mario who says "I have fury" and "be off, awful person", which sounds like "Be a Fawful person).
- When he is fought the second time in Superstar Saga, his battle theme is the same as Popple's, possibly because both are Beanish characters. Interestingly enough, Popple and Fawful's names sound similar.
- Fawful is one of few recurring villains not affiliated with the Koopa Troop. The only other one to appear twice and not turn good was Tatanga.
- Fawful is similar to Dimentio. Both are insane and psychotic, who start out as servants to the main villain and later (in the same game or in a different game) become the main villain. Both have a final form that is combined with an evil object, and both have a similar death scene, spending the last few moments as a head and near death, but trying a last ditch attempt to destroy the main characters. They also share an "always smiling" personality.
- A key difference is that Fawful reappears again while Dementio doesn't.