APPLE.MOV in its entirety. Especially Applejack's apple trip.
However, the Ask Jappleack blog turns that scene into a bit of Fridge Horror
The Mane Six's expressions when Applejack is eating all the apples. Especially how Rarity's eyes do some kind of somersault thing.
Even funnier in "DRESS.MOV", in which Twilight's entire face does the same thing.
"Yo Applejack! You alright?" *gurgling noises* "Yeah you're gonna be fine."
"RARITY! Get your FATASS out here and help me find the elements!!"
Rarity owning a sweatshop full of Mexican workers that make dresses for her and being such a Bad Boss that it goes in Refuge in Audacity almost immediately.
Mexican girl: Mrs Rarity, I'm so thirsty... Rarity: [grabs glass, snorts, and fills it with spit] Drink that, dear.
She also says that Mexicans aren't real people, and when the above girl asks for her pay, she says she can't understand her through her accent.
After a boy named Paco complains to Rarity about his fingers hurting, Rarity responds by magically breaking his fingers, after which Paco says, "Oh no, looks like hard times ahead for Pacooooo!" It's such a cheesy-sounding line that it seems like it should be accompanied by a laugh track.
Twilight: Fluttershy! Have you seen the Elements of Harmony? I can't find them anywhere! Fluttershy: Hey hey hey, I sure haven't, purple guy! Stay out of my shed, okay!
Narrator: So uhhh...what are your rates? Pinkie Pie: 10 for a tuggie, 20 for a blowie, and 25 if the cameraman watches.
While jacked-up on Cocaine, Pinkie Pie suddenly starts ranting on about how she hates internet piracy to two passing bystanders(one of them being Octavia). Blink-and-you'll-miss-it bonus: the other pony's cutie mark is a NERV logo.
Pinkie Pie: "What if Ringo Starr just lobs into your house and stole your...uh...favorite dress?" Octavia: (visibly frightened) "I think I'll mostly be confused?"
Pinkie: Hang on... there's this stupid bitch staring at me... *beat* Oh wait, that's me I'm lookin' in a mirror.
"Hang on, Spike, I gotta go talk to this mirror, I'll call you back." *hangs up*
Twilight Sparkle: Spike, I told you with was an intervention? Where is everypony? Spike: Applejack's in a coma, Rarity's being held captive by the Mexicans, Fluttershy's in the nuthouse and Rainbow Dash is dead. [gets a shit-eating grin] Any more questions, smartass?