It isn't the changing that's worrisome, it's what he might become.
--
A Most Unusual Butterfly
The Doctor felt his face; everything felt strange, absolutely everything. Most disconcerting. Had anything gone wrong? He'd never done this before, and from all the soothing platitudes spouted to anxious first-timers, he couldn't clearly recall a single one.
Butterflies didn't seem this addled when they emerged. Of course, they didn't do it all in one go.
"Mirror," he mumbled to someone, a girl, her name unknown; such trivial details would have to wait for higher priorities just now.
His reflection showed a rumple of shockingly dark hair and a face..well, no butterfly, no. Still… he smiled experimentally.
This would fly.