Robot Unicorn Attack's original web iteration was a moderately funny joke that morphed into an amazingly addictive game, and then morphed into a similarly insanity-fueling mobile game.
Building on the success of the original, Adult Swim Games has made Robot Unicorn Attack 2, which just recently made its Android debut and, happily, seems much more stable and playable than the buggy original.
Rather than trying to explain the sheer madness of RUA 2, we'll defer to Adult Swim's promotional trailer.
Basically, there are hoops, monsters, space whales, and giant star crystals, along with a small army of different unicorns, and an achievement system that actually gives players some motivation to play again later. Oh, and environments that are wildly styled and just distracting enough to sweep you off your hooves every once in a while.
In short, fans of the original will definitely not be disappointed.
If you liked the old RUA, you'll love RUA 2. Even if you didn't the game is free, so it's definitely worth checking out. Be careful though, it only takes one or two rounds to get hooked.