Mad Gasser was inspired by the legend of the Mad Gasser of Mattoon, an urban myth that supposedly terrorized the small city of Mattoon, Illinois by spraying victims with an unidentified gas.
Mad Gasser can be found in Tsukiji Hongwanji during the entrance test presented to Flynn and his fellow Samurai. Flynn will need the Demolingual App in order to communicate with them, but attempting to do so during the trial will result in them blowing on the candle. Mad Gasser can teach Flynn the Shibaboo and Poison Breath skills through its Demon Whisper.
Shin Megami Tensei IV Apocalypse[]
Mad Gasser can be found in Shibuya. He can teach the Bind Voice, Poison Breath and Pandemic Bomb through his Demon Whisper. Mad Gasser benefits greatly from learning ailment skills.
Devil Summoner: Soul Hackers[]
"A mysterious figure that spreads an unknown poisonous gas around. He wears all black and is said to be a tall man. The gas he uses has a sweet smell but inhaling it will cause intense headaches and vomiting. He returns when people begin to forget his existence, though he is rarely sighted."
—Devil Summoner: Soul Hackers compendium
Soul Hackers 2[]
"A tall and foreboding figure clad in all black that spreads an unknown and highly poisonous gas around. Despite its deceptively sweet scent, inhaling the toxic fumes will induce both severe headaches and vomiting. He often returns just as people have begun to forget his existence, though he has very rarely been sighted."
—Soul Hackers 2 demon info
Mad Gasser is faced as a boss during the "Phantom of the Night" request. He can be found beyond the formerly locked door at the end of the East Shipping District. Mad Gasser will frequently used Poisma during the battle, making access to Lourdes Water or the Lourdes skill a necessity, as well as access to healing skills. Ice skills can be used to exploit his weakness to enable a Sabbath at the end of each player turn. Mad Gasser will use Poison Breath the turn after being knocked into low health.
Mad Gasser can be encountered as a common enemy in Saizo's Soul Matrix 1F.
Shin Megami Tensei: Liberation Dx2[]
"A mysterious tall man garbed in black that disperses an unknown poisonous gas. The inhalation of his sweetly scented concoction causes intense headaches and vomiting. He returns when people begin to forget his existence, though he is rarely seen."
The canister on the Mad Gasser's back is labeled G-3, a possible reference to Mobile Suit Gundam, where G3 Gas is an extremely deadly chemical weapon used for massacring entire space colonies.