"Whom Gods Destroy" Season 3, episode 14. This episode features the Chinese grandfather from the beginning and ending of the movie Gremlins! (I only remember that because we watched it in our household very recently.) In this installment, there is a medicine, a drug, for the insane. A previous starship captain, Garth, is now criminally insane, takes over the asylum and now tries to get aboard and take over the Enterprise. All that and the fact that he has somehow learned the trick of becoming a changeling, able to transform his body into the appearance of anybody else; oh yes, and he has a green lady alien as a sidekick. One interesting aspect to this whole mess is the code "Queen to Queen's level 3" that most be answered before beam up. Kirk won't give away the code, preventing the inmates from rampaging all over the ship. My concern is that since this is such a good idea, and also works so perfectly here, wouldn't this become standard practice all...