Past Sins is one of the most popular fanfics in the My Little Pony: Friendship Is Magic fanbase. Months after completing the story, its author Pen Stroke decided to give various writers from the /fic/ board on Ponychan a chance to riff the original, previously unseen and unrevised version of the story. Readers from the Equestria Daily fansite were also recruited to add riffs of their own. The result is an MST, which can be found online.
I'm Standing Right Here: During the scene where Nyx prepares to reveal her wings to the Cutie Mark Crusaders, Crazy56U begins counting how much more uncomfortable things are getting (starting with "Hmm... I can't tell, but I think things got 20% more uncomfortable."). When he misses one point:
RLYoshi: Crazy56U isn't around to say it, so... 70%... Crazy56U: ...I'M SITTING RIGHT HERE, MAN.
Mathematician's Answer: When posed with the question "How does a queen work?", Crazy56U decides to consult an expert. The answer he gets from his (Russian) Magic 8-Ball is "Как мне кажется, да." Or, "As I see it, yes."
Crazy56U: ...that’s the last time I buy a Magic 8-Ball from eBay.
Noodle Incident: Midnight's explanation of why Spell Nexus has only one sister.
Ezn: Good to know. Midnight: Only the one sister. We don't like to talk about... the accident. Nuke.Equestria: Didn't that sister use to be a brother? Lightsideluc: You would have to ask Midnight about that. Midnight: ...don't judge me! intangiblepony: Well, damn, I feel awkward now...
No OSHA Compliance: The Children of Nightmare used a fire-based resurrection spell in the middle of a forest.
Not So Omniscient After All: Despite being a goddess, Celestia still can't figure out what the cultists were doing... even though Nexus explained it to her prized student beforehand.
Obstructive Bureaucrat: "Tonight we, the Children of Nightmare, shall see our queen given life, blood, and a form of her own."
Midnight: I have many forms! Chief amongst them, form 14b, the requisition order for an evil moustache! Lightsideluc: Bah! Everyone knows that form 12A, the requisition form for an evil goatee, is far superior!
Purple Prose: Lampshaded when the bowl and armor in the resurrection spell are "wrapped in crimson flames."
Hellioning: What were they burning with before, burnt umber flames? Nuke.Equestria: It was more of a burnt sienna. Alcoremortis: Ah, crimson, another one of my old enemies. Overused in fanfictions everywhere. Protip: Just say "red". Nobody will think you're a Communist if you do. These are more enlightened times.
Put on a Bus: Pen Stroke, who riffed in Part 1, is absent during parts 2 and 3.
The Quiet One: Compared to parts 2 and 3, Crazy56U was practically silent in part 1.
Remember the New Guy: Some riffers don't start making comments until later chapters, but nobody brings up their sudden arrival. Justified, as sometimes riffers don't show up until some of the earlier chapters have been closed from more comments, so they have to start at later chapters. For example, Wild Trotter showed up to riff on chapters 9 through 13, thinking that the first eight chapters were boring.
Vimbert: TWIST AND SHOUT! Twist and shout. C'mon, c'mon, c'mon, baby now... Alcoremortis: Please. If we're going to start quoting songs... "Let me in, get me out. Can't do more than twist and shout..."
Ezn: And half whispered, creating an interesting vocal effect. intangiblepony: What's with all the half talking? Nuke.Equestria: They're half-decided on what to say. Anon13: It's a half-assed fic. Er, half-flanked.
Near the end of Chapter 10, Crazy56U has the following to say... about one of the riff's own running gags:
Crazy56U: OK, I know Diamond Tiara and Silver Spoon are jerks, but singling them out as the main reason you're now Nightmare Moon? ...I'm shocked that I have to say this, but... that's a little... harsh. RLYoshi: That's not the important part! The point is that they stole cookies! AND. THAT'S. TERRIBLE. Crazy56U: OK, that joke is running thin. Knock it off.
From chapter 13:
CTOONfan1: Especially that one people have been calling SOPA. Crazy56U: Sooooo... Spell Nexus wrote that in this universe... (pulls out shot gun) ...interestin’. (pumps gun)
What Could Possibly Go Wrong?: Lampshaded when Twilight heads back into the Everfree Forest, stating that she knows how to keep herself out of trouble.
Disco! Yet it happens in nearly every episode. intangiblepony: Saying a phrase like that is the same as saying "What could possibly go wrong". Pemberton: Which is proven by how she was kidnapped less than 24 hours ago. Alcoremortis: Personally, I'm a fan of, "There's no turning back now" and talking about the wife and kids in a war movie.
Pretty much any time Twilight does something foolish.
And when Spike is bribed into not revealing Nyx to Celestia.
When it's revealed that Celestia planned on killing Nyx if it turned out she's Nightmare Moon.
Celestia: She is a product of a spell, and well be dealt with as such. She will be dispelled and the lingering energy purified. Crazy56U: So... in other words, you're going to kill a filly to confirm your paranoid suspicions... yeah, um, lady? WHAT IN HOLY HELL IS WRONG WITH YOU?!?
Not to mention this bit (albeit played for laughs):