Just as [Eustace] reached the edge of the pool, [two things] happened.
First of all, it came /over him /like a thunder-clap [that he had been running on all fours]
—and why on earth had he been doing that?
And secondly, as he bent toward the water,
he thought /for a second [that yet another dragon was staring up /at him /out of the pool.
But in an instant he realized the truth.
The dragon face in the pool was his own reflection.
There was no doubt of it.
It moved /as he moved: it opened and shut its mouth /as he opened and shut his.
He had turned /into a dragon /while he was asleep.
Sleeping /on a dragon’s hoard /with greedy, dragonish thoughts in his heart, he had become a dragon /himself.
From The Voyage of the Dawn Treader
Compiled in A Year with Aslan