The Spirit of Chaos, Discord is based on Star Trek: The Next Generation character Q, and voiced by the same actor, John de Lancie. He is a chimera, made up of several mythical and natural animals, including lion, deer, goat, chicken, dragon, bat and bird.
Discord enjoys the idea of chaos, of things happening. The normal every-day routine is boring to him. Though he now tries to be a force for good, things get away from, sometimes literally. Multiple times he tries to help the Cutie-Mark Crusaders have an entertaining day; Discord simply seems unable to understand the Crusaders are children and need calm, cool and collected adult supervision.
Only having recently learned the magic of friendship, he still struggles to grasp some very basic concepts of it, such as having different friends for different things. He was very offended when Fluttershy invited Tree Hugger to the Grand Galloping Gala instead of him, thinking it meant that they weren't friends after all. To get back at her, he invited the Smooze, an amorphous green blob of goo, to the Gala, and tried to make her jealous.
The Return of Harmony pt 1 and 2
Keep Calm and Flutter On
Three's A Crowd
Make New Friends But Keep Discord
What About Discord?
Dungeons and Discords