“Yes, Princess, I’m ready to use my magic for good instead of evil…most of the time.”

“I’ll leave the Elements with you, Twilight…just in case.”

Directly following the events of “Keep Calm and Flutter On” Discord and Celestia call each other out on these little ‘disclaimers’ and try to explain their words while still maintaining their new friendship. They soon agree on some interesting conditions for Discord’s recent reform, leading to the castle, some Royal Canterlot Voice from Luna, cake, and an interesting night and morning as Discord figures out how to relate to his former princess foes in a much less evil (if as obnoxious as ever) sort of way. He especially enjoys his new ‘friendly’ way of bothering Celestia.

Later, following Tirek’s defeat (and Discord’s final reform), the chaos master and the sun princess assess how their friendship has gone and where it might go from here. Luna throws in her two bits as well. Naturally, cake is eaten. And, of course, no matter how reformed he may become, Discord ‘loves’ teasing Celestia as much as ever…and it’s sort of grown on Celestia too.

(Rated Teen really only because of some suggestiveness, and I just want to err on the side of caution :) )