Laughing gas is a form of gas that causes a heightened sense of euphoria in those that inhale it. In the real world, the truest form of laughing gas is nitrous oxide, which is most commonly used as an anesthetic. Popular fiction however has elevated the concept of laughing gas, often times making it a bright, visibly colorful gas that causes uncontrollable fits of laughter. This is most often seen in animated programs, screwball comedies and some comic book based programming.
Laughing gas was but one of many such crazy weapons utilized by the super-villain known as the The Trickster, as seen on the 1990 live-action TV series The Flash. In the series finale, "The Trial of the Trickster", the villain was put on trial, but as always, he had an ace up his sleeve. His loony sidekick, Prank, had a canister of laughing gas hidden inside of a teddy bear in the courtroom during the Trickster's trial. Once the canister was activated, the Trickster and Prank donned special gas masks while the rest of the courtroom gallery burst into raucous laughter.