Episode 7. Man, is it funny to see Orochimaru being wacky and trying to speak English.
Orochimaru: "Yes! I'm a tourist, okay?"
Chapter 27 is about the Akatsuki members going on summer vacation. It's as hilarious as it sounds.
Episode 25 of the anime, where Lee thinks that the writers are changing the show from an action comedy into a romantic drama. A romantic drama skit starts, starring Lee, Neji, Tenten and Naruto...only for it to abruptly end because Lee admits that he's never watched a romantic drama so he has no idea what to do.
Sasuke copying Lee's Sexy Swimsuit Jutsu via Sharingan, much to his horror.
It's even funnier in the anime, where Neji somehow gets roped into it too. And then it's lampshaded that Neji's Sexy Swimsuit Jutsu is anime-only.
Naruto and Lee trying to act like one another in the "Freaky Friday" Flip episode. You know it's a lost cause when the reason why Tenten and Neji wonder if anything has happened to "Lee" is because "Lee" is walking normally.
Naruto(in Lee's body): What kind of life does this guy normally live?!
Lee in Naruto's body is just a goldmine of hilarity. He uses a Transformation Jutsu to change into a Bishōnen version of himself, much to the bewilderment of Naruto.
Naruto: Who is THAT supposed to be?!
He then creates a new technique Monroe Jutsu...which is just him transforming into Sakura to use a Marilyn Maneuver.
He also praises Guy by saying that he'd beat Kakashi hands down in a ramen speed-eating contest and that he's better than everyone, much to the surprise of the former and the absolute horror of the latter.
Kakashi:I've really fallen from grace recently...
Flying Weapons: Breast Hammer!
Lee trying to make a point about White Day via a skit, only for the skit to be so unrelated that even he's not sure what point he's trying to make.
Lee: Wait, what was I talking about again?
In Chapter 19.5, the promo for Naruto SD Powerful Shippūden, the expression on Deva Path's face when Naruto unveiled his Nine-Tails Chakra Mode was priceless.
Pain: Eh!? What is that?! You never used that on me!!
In Part 1 of Episode 51, Sasuke's Kirin originally appears as it usually does the first time he uses it... and then appears as a talking giraffe during subsequent uses.
Pretty much everything about Chapter 32 in the manga, an obvious parody of Naruto High School A.U. fanfics:
Naruto's introduced as the new transfer student and states that he wishes to be the top gang-leader of the school. Then Lee comes in as another gang-leader transfer student...
Naruto:We don't need two gang-leader transfer students in one day!
Lee: That's so unfair! I wanted to be the gang-leader character!
Both Naruto and Lee try to initiate a Crash-Into Hello with Sakura. At break-neck speed. It's as if they took a page out of Maki Natsuo's book.
Round the corner and BAM!
Sasuke trying to act cool despite stepping in dog shit.
Hinata gets the courage to tell Naruto how she feels.
Hinata: P-Please take this! (hands Naruto a letter)
Naruto: Hinata...could this be...I see...I think I understand how you feel...
Hinata: Eh! Th...then...
Naruto: Yeah...Bring it on!
Hinata:No, Naruto, this is a love letter!
Neji as the Student Council President. He deals out reasonable punishments to Naruto for breaking the school rules, but the last one...
Neji: And this, by far is the most unforgivable...write "I will always and graciously accept letters from the beautiful and refined Hinata-sama" one million times!
Naruto:Is that even a school rule?!
Playing soccer causes all of the guys (and Akamaru) to develop some tall and disturbingly well-toned legs while still keeping their super-deformed upper body.
Tenten:That's all they did?!
Lee somehow getting the entire Hyuuga clan to do a Harem Jutsu...with most of them liking it, much to poor Neji's bewilderment.
Neji:Is this the dawn of new age for the Hyuuga Clan?!
In the same chapter, we have Hanabi demonstrating the strongest technique that she learned from Hiashi...which is just combining the Eight Trigrams with Hiashi's stinky socks.
Tenten's stint of acting as Tsunade in chapter 36. It was almost as if Tsunade wanted people to notice that she's gone. While her first two appointments she has to do for Tsunade are funny in their own right, her last appointment takes the cake. The appointment? Meeting up with Jiraiya and Orochimaru for lunch.
Orochimaru's outrage to why "Tsunade" wasn't affected after he spiked the alcohol with a drug.