DELETED SCENE:
When I first wrote this story, I had this scene at the end, because I thought it was funny (What can I say? I'm a fan of Trollestia). Then I decided that it was overkill and made the ending sound like it was rambling, and so I deleted it; leaving Celestia's presence just implied. A couple comments later, I realized that my implying skills need work... So I decided to post it after all.
Late that night, Rainbow Dash threw herself on her bed (obviously, also made of cloud. Cloud, cloud, cloud... Rainbow loves clouds...). The after-party was, as expected, crazy. Then again, it had been her idea to invite Pinkie Pie.
Totally worth it, though.
She was wondering how exactly Pinkie had gotten the party cannon up there on the clouds when she had arrived by teleportation when she heard a voice call her name. “Rainbow Dash....”
Rainbow sat up and looked around, confused.
“Raaainbow Daaash....”
Rainbow Dash shot up into the air, all thoughts of sleep gone from her mind. “Wh- Who's there?”
After a moment of unnerving silence, the white pegasus from before walked into her room. “It's just me.”
“Who are you, and what are you doing in my room? And how did you get in here?”
“Oh, don't mind me. I just came to congratulate you again on your promotion.”
“And you couldn't have done that earlier?”
“Oh, I like doing it now. I always keep a close eye on all the Wonderbolt Captains.” With a quick, powerful flap of her wings, the white pegasus flew up to meet Rainbow's eyes. “You could say it's part of.... my tradition.”
“Your tradition,” Rainbow Dash said flatly.
“I'm watching you, Rainbow Dash. Always watching you.”
Rainbow Dash probably should have been afraid, or something, but her mind was already overtaxed and running very slowly, and gave her no response. She just stared, confused.
After a minute of silence, the white pegasus's face fell. “You're no fun,” she said, shoving Rainbow playfully. “Spitfire screamed like a schoolfilly. The one before her was still drunk and tried to hit on me.”
Rainbow's sluggish brain was working overtime to make sense of that part. It came up with “potato”, which led Dash to believe that she had missed something important somewhere.
The white pegasus landed and turned to leave. “Honestly, I think you'll do a great job, Rainbow Dash. Congratulations. You deserve it.”
Rainbow's mind was still processing as she walked out the door. Something was different about her voice that last time....
Wait.... That was Celestia's voice!
She flew out of her room, but her house was completely deserted.
“When you least expect it, Rainbow Dash, I'll be there.” Celestia's disembodied voice rang through the air. “That's a promise. And you know that I always keep my promises.”
Rainbow Dash shuddered.
“Sleep well, my little pony.”