After Jean-Luc Picard dies, Q goes into a fit of despair and begins to wander the universe in search of a new purpose. Having considered Jean-Luc his 'project', he craves a new one, but worries that he might never find anything nearly as captivating.
Then he finds a Class M planet that holds a bizarre country. Equestria. Jean-Luc would have loved it, he's sure...
Taking it upon himself to judge the pony species' right to existence, he displays himself to the masses as a draconequus, not realising that the beast is known in this world as a god of chaos.
So begins the dawn of the rule of Discord.
NOTE: This is a Q-becoming-Discord deal, just to clear that up.