1 Lambert: Mordekai, your turn. P. And piercer’s not allowed, since we just mentioned that.
2 Mordekai: Purple worm.
2 Kyros: Q? Quasit, obviously. Not a lot of choice, is there?
3 Mordekai: What about quippers?
3 Kyros: They’re just piranhas with a stupid superfluous name.
4 Kyros: Like someone had taken demons and decided to call them... I don’t know, tanar’ri or something for no reason.

Quasits are small minor demons original to Dungeons & Dragons. They sometimes serve as familiars to evil wizards.

Quippers are exactly what Kyros says, piranhas with a superfluous name. Piranhas are a fine type of monster to have in a game, but they are more fear-inspiring if you call them piranhas rather than a made-up name that gets the players wondering what they are and then wondering why they aren't just called piranhas.

D&D has had demons as monsters ever since the original edition of the game. However, with the launch of the Second Edition in 1989, the name "demon" (as well as "devil") was dropped from all rulebooks, to be replaced by the invented term tanar'ri (and "devil" was replaced with baatezu). This was a reaction to the "Satanic panic" moral panic of the 1980s, during which some people associated the game with Satanism, witchcraft, suicide pacts, and other morally reprehensible things. A major activist was Patricia Pulling, who formed the group Bothered About Dungeons & Dragons (BADD) and campaigned to have the game banned on the grounds that it was corrupting youth. Various Christian groups also campaigned against the game, claiming that the use of demons and devils as monsters indicated that the game was morally corrupt and dangerous.

Despite these campaigns, the game remained popular and continued to sell. However, the publisher TSR decided to sanitise the game of demon and devil references by changing the names in the Second Edition, in an attempt to circumvent any future damage. The move was unpopular with fans of the game, being called a "sell-out" to conservative religious pressure. In attempting to pacify outraged fringe campaigners who didn't even like the game, TSR alienated some its most loyal fans. (This wasn't the blow that drove the downturn in roleplaying games in the 1990s though - that was driven by the pressure of competition from the rise of computer games and collectible card games, the latter led by Magic: the Gathering, which also saw a similar conservative backlash against demonic imagery but ultimately overcame it.)

Demons and devils returned in name in the Third Edition of Dungeons & Dragons in 2000, and publications of this edition reconfigured the classification system used to describe various groups and levels of demons and devils. The name tanar'ri became the name of the subset of demons that form the core group of demonic monsters in the game, in contrast to another group called the obyriths, a primordial and more ancient line of demons whose heyday has passed, leaving them as scattered remnants of their former power. There's also a more recent group called the loumara. In a similar manner, baatezu has now come to refer to the ruling subgroup of devils.

This categorisation has persisted through the Fourth and Fifth Editions, into the current resurgence in popularity of the game.