It Takes a Village/Funny

"Rainbow Dash: Hey Spike, you made a totally awesome splash when you hit the water!...At least you kept your rump up! Spike: Hooray for me."
 * Spike’s first flight lesson in Chapter 4

"Spike: You lied.
 * After his second attempt also ended in failure, we got this:

Rainbow Dash: Sorry... (tries muffling her giggles with one hoof)

Spike: You've killed me.

Rainbow Dash: Hey, if you will insist on falling...

Spike: Breaking News at Ten: Wonderbolts Star Finally Cracks. Crazy Pegasus Kills Incredibly Handsome Young Dragon Stone Dead.

Rainbow Dash: That was a pretty wicked somersault you just did.

Spike: "Eyewitnesses Say; 'It Was a Pretty Wicked Somersault'."

Rainbow Dash: "Additional Report: Dragon Blubs and Moans Just Like a Little Filly.

Spike: "Policeponies Warn That Pegasus Is Obviously Deranged and Dangerous. Do Not Approach.

Rainbow Dash: Dragon should get his backside back up that hill and have another go.

Spike: Pegasus loves to see Dragon suffer."

"(Spike drags himself out of the water, and coughs up a fish. Dash takes one look at him and keels over laughing)
 * I thought this was hilarious because both characters are pretty much Deadpan Snarking each other in third person.
 * And after trying again for a THIRD TIME, and failing, we got this:

Spike: Glad... it's so... amusing...

Rainbow Dash: Sorry... ahahahah! Aha... ahuh... hummhmm..."

"Scootaloo: In case of emergency, don't – and I repeat don't – jump off Spike. We have a unicorn standing by if he hits a sudden downdraft or something... Spike: I'm fine with downdrafts. Scootaloo:... but she can't catch all of you and a dragon, so just stay put. Keep your seatbelt on at all times, and the pilot better not tell you to take it off, otherwise he's lookin' at a tail-kickin'." Spike: Who gave you this job anyway?
 * In chapter 10, Spike finds out that Sapphire Shores wrote an overly sappy, sad song about him called “Full of Fire.” Spike’s initial reaction to this is, hiding himself under his wings forever to hide himself from embarrassment. But what really makes this so funny is Twilight and the others reaction.
 * The chapter with the Gala includes Applejack and Rainbow singing the song. Very loudly. While completely pissed. The rest of their drunken arguments count as well.
 * When Spike is giving air-rides to some ponies, Scootaloo tell the passengers what the rules are. Needless to say Hilarity Ensues

Scootaloo: I volunteered. Now, shhh. Please keep your hooves close to you at all times, and please don't tickle the pilot mid-flight."

Spike : Did you make all this up too?

Scootaloo: I'm doin' my civic duty.

Scootaloo: Cheering, whooping and yells of 'YEAH!' are strongly encouraged, and you may talk to your pilot as long as he's not bein' a grumpy-pants. Which he is, so don't talk to him.

Spike: You are in so much trouble.

Scootaloo: "Full of Fire,” Spike.

Spike: I hate you.

Scootaloo: I know!"

"Spike: I thought I burned all of those! (talking about his baby photos)"
 * When a newspaper article about Spike comes out, there's photo of his newly-hatched self, stuffing his tail into his mouth. His reaction to it is priceless:

"Fluttershy:You're soooo cute. Widdle baby waby Spikey-wikey. Spike: Must you? Twilight: Well, you were cute. Pinkie Pie: Cute! Rainbow Dash: Sorry, Spike, you were cute (snickers) Spike: Oh, shut up."
 * Don't forget the others reactions:

"My ponies! Muaahahah! Mine, all mine! M-my p-ponies! Mine? Please? Maybe one? Just one? Just a little one then? How about a background one? Aw dammit. Selfish Hasbro."
 * In the epilogue, Spike couldn't get through the courthouse door, and his hindquarters were left sticking outside for the whole of Canterlot to photograph.
 * It doesn't help that, Scoop Headlines had won his third Ponitzer Prize that year, with an article featuring a picture of Spike's scaly rump.
 * The author puts rather hilarious disclaimers at the start of the chapters. One example, from chapter 7:

"Pinkie: I found them! Fluttershy: Is Applejack...drunk? Pinkie: Of course not, silly. She's plastered. "
 * The Epilogue reveals that Twilight has spoken extensively with the Magician of Coal Crater, and was excited to learn that he is old enough to have personally met Starswirl the Bearded, one of her heroes. What the Magician has to say about Starswirl, however, is something of a disappointment for her...
 * Applejack and Rainbow get drunk at the Gala. Every part of their antics is hilarious, from Pinkie's announcement of their states...

"Rainbow Dash: He's...so...grown-up...You are...you are, you're so awesome it totally and completely and totally and totally boggles my mind. You boggle. BOGGLE. Best dragon ever. Ever. You...you're the best...You're the besht."
 * ...to Rainbow bawling over how "awesome" Spike is...

"Pinkie: Oh, oh, oh, I know! We've got Rainbow Splash! Spike: Appletanked. Pinkie: Rainbow Sloshed! Spike: Dash of Spirits! Pinkie: Applejack! Spike: (Beat) I got nothin'. Pinkie: Appletini still works.
 * ...to Pinkie and Spike thinking up nicknames for their inebriated friends...

Spike: I was trying for new material."

"Rainbow Dash: Hey, look, AJ! It's Sapphire Surely! Applejack: It's Shores, yer silly filly. Rainbow Dash: Oh, whoops. Sorry, Miss Surely. Applejack: Shores. Rainbow Dash: That's what I said! Your ears are drunk. Applejack: Mah ears ain't drunkerer than yer mouth."
 * ...to them disagreeing on how to say Sapphire Shores' name.