"Sit down Twilight, I've got something to tell you." Twilight turned in shock as Spike sauntered into the library and sat himself down in front of her. "Look, there's no easy way to say this, but I'm really Princess Celestia!"
Twilight gasped. "What! I mean I guess that makes total sense and was obvious in retrospect, but what?"
Spike nodded. "I had to keep an eye on you, my daughter who I fashioned from clay. That is why you never saw us in the same place, apart from all the times you did. When you give me a friendship report, I actually read it and then burnt it up."
Spike leaned back in his chair, a magical white horn appearing on his head as he revealed his true powers. "You see Twilight, I had to keep you close since you will replace me as the next magical princess, and the only logical way of doing that was to disguise myself as a small purple dragon."
"But what about when I hatched you from an egg and Celestia was right there?" Twilight gasped.
Spike looked smug. "See, that's just how good I am!"
Twilight furrowed a brow. "But what about the huge crush you have on Rarity?"
Spike sighed. "Rarity is my magical clone, of course I would feel attracted to her. Ponies always feel attracted to their magical clones, that is why Scootaloo likes Rainbow Dash so much." He coughed, large white wings unfurling from his back. "But now my deception is over and there are no secrets between us!"
"Not so!" Twilight rose to her full height. "You see, I am ALSO Princess Celestia! From the future!" Magical wings also unfurled from her back and Spike gasped. "So you see Spike, it was really me who was in control all along!"
"Not so!" came a cry from the far end of the room. Both faux Princess Celestias turned to see Owlowiscious. A horn appeared on his head. "I am Princess Celestia from the DOUBLE FUTURE!"
And so it went.