ScrewAttack has posted an in-depth article concerning the various mini-games that have been found throughout the history of the Mortal Kombat series. Since the early days of the series in the 1990's, Mortal Kombat has always included fun bonuses to entertain players. It began with the Test Your Might mini-game in MK1 and continued with in game versions of Galaga and Pong. With the evolution of the sixth-console generation, the MK team began to expand these games from simple time passers to full fledged modes of their own. Our first taste of this was in 2004's Mortal Kombat: Deception which gave us both Chess Kombat and Puzzle Kombat. Motor Kombat came with Mortal Kombat: Armageddon. The side adventure game Mortal Kombat: Shaolin Monks had a special versus mode apart from the main game as well. From the article:

I'm a big fan of puzzle games. I believe that Tetris Attack is possibly the greatest puzzle game ever made, and I once skipped school to beat someone's score in Popcap's Alchemy so they would stop bragging. So it should be a surprise to no one that I viewed Puzzle Kombat as an equal to the Transformers delivering me gold bars while I'm accepting honors for writing the greatest novel in history - and watching Black Dynamite at the same time. I loved this game, and I still do.

This mini-game takes the idea of tradition chess and takes lots of liberties. You still have differing pieces, but the pieces are very unusual. You have your usual pawns then sorcerers, shifters, champions, and a leader(king). A round of Mortal Kombat is played each time two pieces meet in a square, and that's where a lot of the differences in pieces show up.

Shaolin Monks' Versus Mode was the closest thing to taking MK to true 3D. The process behind it is simple: Shaolin Monks takes the best of MK to open 3D, non-round combat. The Versus Mode takes SM(Shaolin Monks), narrows it to an arena - or stage - and brings back traditional, best of three combat. The best way to describe this is to compare it to the cult classic fighter Ehrgeiz.

The last yet most recent mini-game I'm going to mention is a ripoff of a very famous franchise but still ridiculously fun: Motor Kombat. Take Super Mario Kart, restrict the number of tracks(it is a mini-game after all), add in the madness that you expect from Mortal Kombat, and you've got a badass mini-game. Motor Kombat features special moves, death traps, multiple characters, shortcuts and more.