The ball of light dissipated, leaving Twilight where it once was.
"Twilight!" Spike ran up to the mare. "Twilight, you're... an earth pony?"
"Whuh?" Twilight tried to light her horn, but nothing happened. Because it wasn't there anymore.
"That'll teach you not to screw around with ancient magic." Celestia landed in front of Twilight in a... not-so-graceful manner. She dusted herself off with her wings as she climbed out of the crater she left in her wake, and pointed a hoof at Twilight. "No horn rights for you!"