In a flashback, each time Jack suggests that New Directions sabotage their competition, Will seems to cut him off faster each time. This is made funnier by the sheer fact that Jack doesn't seem to understand how Will is able to anticipate his suggestion.
Jack's opinion on Mitchell wanting Quinn and Rachel wanting Finn, referring to the former as a "poorly done production of Phantom" and the latter as a "demented version of Twilight which is redundant."
Mitchell turning into a hippie after taking all of his anti-anxiety medication in one sitting during "Funk"
Mitchell (Age 6): "AAAAHHHHHHH!" a six year old Mitchell ran through the dark house, screaming, "THE MAN WITH THE KNIFE HANDS! FATTY COUGAR'S GONNA KILL ME IN MY SLEEP!"
Then there's the classic Mr. Schue hallucination of the ND kids as little kids with Little Quinn and Little Sam getting dialogue and Little Jack, Little Mitchell and Little Michelle added to the mix. Funniest and cutest hallucination ever!
Mitchell launches himself into the fight against Karofsky in "Furt" with "MORTAL KOMBAT!" Unfortunately, Mitchell misses and knocks himself out by slamming into a locker behind Karofsky.
"What in the name of Apple Brown Betty are you doing?"
Puck's performance of Cherry Pie is pee-inducingly funny.
He's Alive/Through Our Eyes
Dylan and Jack's flashback to when they broke into Dustin Goolsby's office
Jack's logic behind kissing both Sam and Santana in He's Alive's version of "Rumours"
Jack: If anyone kisses me and isn't turned on, you're not gay...or straight.
Dylan trying to get through to Quinn during her time with the Skanks.
Dylan: What happened to you, Quinn? When you left for the summer, you wanted a change in your look. I understood that and now it looks like you've been dragged through a hedge backwards, that's been covered in pink paint. And what the hell is this about you dating a 40 year old skateboarder you met at a truck stop?!
The inference that Jack and Jenn started the whole "Why is the T-Rex eating the Jew?" comment.
Jacob Ben-Israel being referred to as a ''buck-toothed human bottle opener."
Pretty much anything that happened in the Harm Co one-shot.
What happened to the rest of the club when Quick and Finchel steal their keys and lock them out of their hotel room for the night
Puck: Oh, I see how it is. You commit a couple of misdemeanors, some destruction of private property, a New Year's bullet falls on the neighbor's dog, and, suddenly, I'm the bad guy whenever something happens.
The Benefit of the Doubt features a scene where Mike is almost attacked by a lion in Daniel's house. Daniel keeps it for the day he can use it on Finn. Made even funnier that the the lion's name is Bás, which means "Die" in Irish.