Did you consider making a "Scooby-Doo" ending?:
[The Mane 6, Apple Bloom and the actual Spike (who we just found out was tied up and gagged in a closet while this impostor "Spike" was running around screwing all the other fillies]
TWILIGHT: Now that we've found the REAL Spike, let's see who's behind the mask...
[Twilight uses her magic to pull the mask off of "Spike", only to reveal underneath...]
TWILIGHT: (gasps in surprise) Jinkies! It's...
ALL (IN UNISON): Cranky Doodle Donkey!
CRANKY: (exasperated) Alright, fine, I admit it! I did it all!
PINKIE: But why, Cranky?
CRANKY: Aw, heck, I just wanted to recapture my youth, and live a little bit. Since Spike was coming of age, I figured I could trap him in a closet, disguise myself as him and have my way with as many fillies as I wanted!
[Cut to Cranky greedily looking inside a treasure chest, which emanates a golden aura from its opening.]
CRANKY: And, while all of Ponyville was busy being mad at Spike, nobody would notice the stash of gold doubloons I found behind the old abandoned amusement park!
TWILIGHT: Well, I suppose that wraps up the Case of the Rapacious Reptile!
PINKIE: Yup! I guess we'll be DRAGON him to jail now, eh?
[Pause, 4 seconds. Nopony responds, except for Twilight, who steps in closer to Pinkie]
TWILIGHT: (whispering to PINKIE) Goddamnit, I hate you.
SPIKE: Spikey Dikey Dooooooo!
[Everypony laughs, and freeze frame. Cue THE END.]