Hilarity is a neuro-chemical weapon.
A drug that can be distributed through a syrup or gaseous form. The drug functions by triggering the laughter response in the body, and not letting up. Thirty or forty seconds after exposure, the subject enters a state of intense laughter, causing suffocation. The drug has a number of purposes, depending on dosage. It can be used as a chemical agent for the military, a recreational drug, or used to sedate patients and give them an enjoyable ride to such a state. This drug works on Nepleslians and Geshrin, however it does not work on Yamataians and Nekos due to their digital brains.
However absorbed into the body, this drug affects the section of the brain that produces laughter. This triggers uncontrollable laughter and a sense of euphoria for no obvious reason. It's effects will last depending on the dosage given.