Derpy and the princess took off into the sky with Red Rover and his helpers right behind. Unluckily they were under the clouds so the ponies below could easily see them. Suddenly a red blur crashed into Derpy sending her falling downwards. She flapped her wings trying to regain her flight but instead she hit the ground and dust flew upwards.

She heard hooves hitting the ground. She opened her eyes to see a brown earth pony looking down at her.
"Are you ok?" He asked. He had an accent not much different to the farm pony Applejack's. Derpy stood up and brushed the dirt off.
'What's you're name?" She asked.
"Call me The Doctor." He replied smiling. He held out a hoof and Derpy shook it.
"Nice to meet you Doctor." She said.
"Did you happen to see a pony named Red Rover on the way here?" He asked. Derpy nodded.
"Yeah. How come?" She asked trying not to sound nosy.
"Well he's an alien who is trying to take over the world." Derpy looked confused.
"He's an alien inside a pony, on a different planet, in a different universe." He explained. Derpy nodded to show she understood.
"Could I help you stop him?" She asked. The Doctor nodded.
"I actually know how he became a pony because it happened to me. I came to this world and... now I'm a pony." He told her. There was a noise from overhead as Princess Celestia, followed by Red Rover and his helpers, rushed past.
"Come on!" Shouted The Doctor. He ran underneath them as Derpy flew up behind them. They were about to enter a chase.