The hypnogas is an invention by Tuskerninni. When sprayed on people, they become what they are dressed as. Left on their own, they generally keep their fashion-based actions lowkey, but the hypnogas also makes them vulnerable to suggestion as to how they should perform their dress-up identity.
Tired of losing control of planned-for scenarios because of the element of individual independence, Tuskerninni developed the hypnogas to keep all his involuntary actors in line. The hypnogas is a green-colored substance that influences its victims to believe they are what they are dressed as. There is no known wear-off time but redressing to one's own, regular clothes sometimes breaks the trance. At other times, such a change of clothes will only change the role but not snap the victim out of their daze. Similarly, being dressed as oneself grants a chance at immunity from the gas, but it's no guarantee. An extra effect of the hypnogas is that people become receptive to instructions what their role entails. Tuskerninni went for this effect to cast himself as director, but anyone can provide the scenario and the victims will adhere to it.
To test the hypnogas, Tuskerninni uses it on a taxi driver and has him steal stuff at the mall under the belief he's collecting his fare. When he returns with the loot, Tuskerninni has him dress up as a caveman in a costume treated with hypnogas. The man begins to act exactly like a caveman. Elated, Tuskerninni calls for a screen test. There's a School Masquerade Benefit soon, which is the perfect opportunity to use the hypnogas on a larger scale. The gas is smuggled inside in tanks that are part of his penguin minions' diver disguises and after waiting for the donation pot to fill up nicely, they start spraying the guests with the hypnogas. Tuskerninni manipulates them to hand over their jewelry and other valuables and sets them up against Darkwing Duck who coincidentally is present before making off with the entire loot. Darkwing figures out that the guests are made to act as what they are dressed as and that they are sensitive to suggestion, so it takes him little effort to get the information he needs to go after Tuskerninni. Inside the villain's warehouse, things go wrong when Darkwing attempts to use the hypnogas on Tuskerninni but instead has the canister blow up on him. Darkwing, Tuskerninni, Launchpad, and the penguins become surrounded by hypnogas-treated clothes, leading to a fight of fluctuating identities. Gosalyn takes a stand when they are all in golf outfits and harmless. She manipulates her father back into a Darkwing Duck costume and he snaps out of the trance. With the villains still in it, it is easy to arrest them.