Most of what Seaty Belt/Thrackerzod says in the final scene of episode 10 is hilarious, due to how badly the apparently normal pony... thing... blends in.
Twilight explaining herself to Celestia on Ep. 8. Even more funny thanks to the return of The Rubber Ducky Song.
Twilight: Noooo, noo, that was wrong! So wrong!
Spike's "They threatened me with Tiny Hammers!"
"I think a tiny, evil creature is living in my attic. It likes geometry. And Satan."
"Call of the Cutie"
Applebloom "persuading" Doctor Whooves to buy some apples.
Applebloom: How would you like to buy me some ice cream* Applejack promised her ice cream in exchange for helping out?
Doctor: (backing away) Sounds illegal...
Applebloom: Are you sure you don't wanna buy me any ice cream? Because I am the perfect height to reach your dangly bits, and I think we both know what I'm implying here.
Doctor: (getting nervous)Look, I'm really busy right now and I'm doing something really important. I have to save a kitty named Mr. Fluffles from certain doom.
Applebloom: Do not make me get persuasive with you!
Doctor: (panicked)Stay back! I can travel through time!
Applebloom: Well, good, you're gonna need that power, because I am about to kick your dick into last Thursday!
Doctor: Okay! Just take the money and leave me alone!
From "Rainbow Dash Presents":
From Rainbow Dash PresentsCupcakes. It starts with Rainbow Dash deciding to put on a gorilla suit after reaching Sugarcube Corner and spirals into hilarious madness from there.
Rainbow Dash goes to get a glass of water for Pinkie Pie. Literally one second after disappearing into Twilight's kitchen, she does something to set off the smoke detector. And then a jackhammer. And then machine gun chatter, complete with muzzle flash. And finally, a barking dog.
Rainbow Dash (off-screen): Twilight, do you have any ketchup?
Celestia's last assignment and the "lesson" Twilight learned from it:
Spike: So, hey, you remember that letter she [Celestia] sent you where she asked you to get those pictures of Applejack's brother? Twilight: Yeah. Spike: And then she told you to write a critique of Mac's physical appearance? Twilight: Yeah Spike: And then she sent the critique to Mac? Twilight: (Levitates a drink into her hoof) Yeah. Spike: What'd you tell her you learned from that? Twilight (In a Monotone): A Phillips screwdriver is persuasive, but not seductive; and also Rarity charges out the butt for stuff I really think she should do as a friend.
"Investment Losses"
Twilight and Rainbow Dash on the cloud from "Alicorn Day", when suddenly Twilight's wings disappear and she falls through the cloud.
Aurora on the bus:
Aurora Excuse me, weird adult talking to a kid. I'm supposed to avoid Stranger Danger situations. For that I need a pretty wide bubble without any strangers in it. Now, are you gonna have a Stranger Danger situation? *the adults move* Thank you! I can tell by the lack of proximity to me that you are probably OK adults.