Originally "Munchkins" were those little guys in "The Wizard of Oz" who are so happy after the house has landed on the Wicked Witch of the West (or East? or North? I'm damned if I still know...).
Among people who play role-playing games, "Munchkin" seems to have another meaning, though. "Munchkins" are players who only seek their own benefits. They are not above betraying or even back-stabbing the other members of their party. While that's a bad trait in a role-playing game, it's the goal in the card-games of the "Munchkin"-series.
Actually, the goal is to reach level 10 before the other players. Every time the player kills a monster (monsters are door-cards - there's door-cards and treasure-cards in the game), he gains a level. Being defeated by a monster usually means loosing a level - and other things ... terrible things. Death, on the other hand, is not final. But that is not all the game play. There's other cards around, too. Some are for use - abilities, weapons, armour. Others are to make gaming easier - or harder. There's curses and traps and ways to make a monster more powerful or weaker (depending on whether you're going to attack it or somebody else is - back-stabbing, remember?).
Currently I only own "Munchkin Bites!", the horror-variety of the game. The original "Munchkin" is situated in the dungeon-world of the average role-playing game, but the series also includes games set in space ("Star Munchkin") or in the Far East ("Munchkin Fu"). There's spies ("Munchkin Impossible") and even superheroes ("Super Munchkin"). Unlike with other series of games, though, all "Munchkin"-varieties can be thrown together to create a high-elf-vampire-catgirl with a laser sword or something like that. There's a basic variety and at least one pack of additional cards for every variety of "Munchkin".
The game itself is easy to play, but fun. It's the right thing for people who usually spent evenings for weeks on end to finish their latest campaign of role-playing.
What originally got me interested in the games, was the fact that role-playing guru Steve Jackson had the original idea and John Kovalic, creator of "Dorktower", did the graphics of the cards. The game itself really is fun and quick enough to learn, too.
And, of course, there's a little Munchkin in all of us...