These wacky microgame collections starring Wario and friends have you racing against the clock and trying clear as many stages in a row as possible. In Japan, the series is known as "Made in Wario".
Each WarioWare game is made up of tiny games called "microgames". As the name suggests, these are smaller than even minigames, and generally last only a few seconds. They are played randomly one after another, and the speed is gradually cranked up, until the player faces a "boss" game, which generally lasts longer, more like a typical minigame. Most microgames also have three difficulty levels.
There are currently 1775 different microgames across all titles (as of WarioWare: Get It Together):
Each title in the series is usually made up of several story stages - a set of microgames based around a gameplay mechanic or genre, and wrapped with a character's story. Upon completing all such stages, mix modes are unlocked which allow the player to play an endless mix of all the microgames.
In most games, the player can choose to play a single microgame on a loop, progressing through each of the three levels at increasing speed.
Each game contains a variety of unlockable bonuses. In addition to more fleshed-out minigames (including the Pyoro subseries), there are toys and music tracks to play with.
Game & Wario is an exception, featuring 16 minigames rather than microgames while retaining the quirky style and humor of the WarioWare games. The "GAMER" mode does include a selection of traditional microgames, however.
The handheld games have never included traditional multiplayer, but often include a console-sharing mode for two people (where both players use the same console to play). However, the home console games have all featured dedicated multiplayer modes, often using a pass-the-controller format.
The concept of microgames began in Mario Artist: Polygon Studio, released for the Nintendo 64DD addon in Japan. Players could create their own 3D polygon models and use them in a series of eight "Sound Bomber" games that were just 3 seconds long and got progressively harder, much like WarioWare's games. Those original games were adapted for the original GBA WarioWare, and the boombox motif used in that game is a callback to the Sound Bomber mode.