*Twilight Sparkle head was a teapot.

This wasn't some clever metaphor, meant to provide imagery for something like a fit of rage or a propensity for whistling. Twilight's head was, quite literally, a teapot. And it irritated her.

It had started about two minutes ago. Twilight had been studying, which was normal. Suddenly, she had a strange headache. The next thing she knew, Spike was freaking out. She looked at him, and the hot tea pouring down on him from where his nose normally was did nothing to improve her mood. A quick glance in the mirror revealed exactly what had happened. His usual cute little head had been replaced by a purple teapot, with his face in front of it, and try as she might, her magic wouldn't fix it. She was about to start frantically searching the magic books for a solution when the door to her house burst open. It was Fluttershy, who had three heads*