We're not sure if this line was exactly the same in the original, or even if it was really supposed to be funny, but this line of dialogue from the dub was just begging to be added (especially thanks the completely serious way it's said):
Leeron: Honey, you couldn't handle my creepy toys.
In episode 1, Kamina tries riding a massive herd of molepigs to the surface. It goes about as well as you'd expect.
The uncut version of episode 6 — the obligatory Hot Springs Episode — is absolutely freaking hysterical from start to finish, as it is literally all about Kamina's mission to see Yoko's bare breasts. Highlights include, but are not limited to: Kamina throwing hysterical screaming fits of rage every single time a chance to see the girls naked is snatched away from him; Gimmy sticking his finger up Simon's bum when ordered by Kamina to "find a hole", sending Simon flying into the air and thus able to see the nude girls for a split-second — the sight of which prompts Kamina to smack his own bum repeatedly while demanding that Gimmy stick a finger in it; Kamina's success in eventually getting Simon to join him as an enthusiastic participant (drilling a hole in the wall while singsonging, "Drill drill drill drill..." no less) in the quest to see Yoko's breasts... and that's not even half of it.
What it appears Simon's doing before the camera pans back to show his drill...
"I saw... down to their shoulders!"
In Japanese, Simon just says that he won't forget what he saw. The dub line is almost funnier in that Simon stating he only saw down to the girls' shoulders is enough to incite Kamina into trying to get a peek.
The aftermath of that episode's battle. Yoko jumps up and down while the girls are cheering, and after a whole episode of it stubbornly staying on, her top flies off... to the Awesome Music usually reserved for awesome drilling-through-stuff moments. Even Lagann sports a hilarious expression.
"Ohayo gozaimasu." / "Good morning, sunshine!"
The cut version is pretty funny too, especially the scene where almost everyone is crammed into Lagann. That includes Yoko and the Black sisters. In skimpy swimsuits. Just look at Simon's face when all the boobs (and one ass) are practically shoved right next his face. He's in pure bliss, and it's no coincidence that the resulting Beam Spam is bright pink rather than the usual green.
Not to mention Leeron's reaction to Gurren Lagann's drill poking through the top of his seat.
Viral's quote, "PUT SOME CLOTHES ON!"
The show's dub trailer had this text speed past the screen at the end:
"Producers are not responsible for random fits of giddy delirium. Well, okay, maybe we are, since we produced the show that induces said giddy fits of anime induced happiness, but if you watch anime you have to expect that sometimes and we're not paying to have that grin on your face surgically removed no matter what, so there. Remember to eat and take in liquid while watching marathon sessions (defined as non-stop viewing sessions lasting more than 6 hours) and PLEASE go to the bathroom if you feel the urge, that's why they invented pause buttons. Also, chew your food slowly, close your mouth while eating, bathe regularly and always say please and thank you when asking for the creamed corn. Gurren Lagann is a work of fiction and any resemblance to actual personalities is not only purely coincidental, but also indicates that people who see said resemblances are probably living way too deep in their own fantasy worlds. Do not attempt to imitate behavior or actions seen on this show, unless you are a really hot babe who wants to dress up like Yoko, in which case, we're all for it. Gurren Lagann is available at the finest video retailers, if they don't have Gurren Lagann tell them to get it for you. Now!"
"...THEY PUT KITTAN IN CHARGE OF LEGAL AFFAIRS!"
And he knows enough to know when a defendant is getting screwed and why.
Yoko's moment of Hypocritical Humor in episode 12: "What's with those absurd outfits?" (Referring to bathing suits, which isn't so different from what she wears all the time.)
The fact that Yoko's swimsuit covers up more than her actual outfit. The guys are, understandably, disappointed.
Also, when the Black Sisters come out wearing bathing suits. Kittan throws himself in front of them and tries to shield them with his body as the other male members of team Dai-Gurren ogle them. The girls continue talking about the sea, oblivious.
Combined with Mood Whiplash on one occasion. Simon is arrested, and put in those old-school wooden handcuffs, kind of like a stockade. Cut to the wide angle, and we can see Boota is wearing a smaller but otherwise identical pair of cuffs.
Boota's reaction to Yoko's return. Just that shot of him running as fast as he can...
Episode 7, three words: "...Who are you?" The head tilt just makes it.
Also from Lagann-Hen. During the redone dream sequence, Kamina and Simon are chatting away, when Kittan pops out of the box, saying "Hey, hey, don't forget about me!" There's a pause where both of them stare at Kittan, and Kamina breaks the silence with a quirky "who are you again?" with the above-mentioned head tilt just adding icing on the cake.
Parallel works 2. Epic pachinko. It's especially hilarious how Yoko, Simon and Kamina get into it. Then there's Leeron looking like he's having an orgasm for no apparent reason.
This summary of the series is hilariously spot-on (ads NSFW).
An attempt in the manga to reverse the combining process. Kamina tries to create Lagann Gurren, which involves Gurren balancing on Lagann... which is then crushed under its weight.
In any other context it would be a Tear Jerker, when Nia rejects Simon when he proposes to her, as she doesn't fully understand the question at the time. But in this series, the total Mood Whiplash makes it hilarious. Romantic music plays, Simon and Nia are looking over the city as Simon says it's time to move on from their former identities and truly be together, he pulls out the ring, says the actual words, they look into each other's eyes..."NO WAY!"
Episode five, an otherwise gloomy episode, has the little gem of Kamina taunting Rossiu. Father Magin just carries on lecturing while Kamina chants "Man or mouse? Man or mouse?" in the background, oblivious.
Kittan's attempts at interrogating Nia, which quickly become clear to have about as much likelihood of success are interrogating something that can't talk. Kittan demands information, and Nia asks why he thinks she knows anything, to which he replies it's because she's the enemy, and Nia asks him what's an enemy. Kittan says it's someone who pisses you off, and then Nia asks him WHAT THAT means, and he's got no reply apart from rage.
Leeron once scared Gimmy off of his computer by making a hideous face and saying "I'll eat you!"
Kamina trying to pull his sword on Leeron when he hits on him.
Yoko's Yaoi Fangirl moment in episode 3. Just look at her face after Kamina says "Gattai da!" Twice as funny when you see her disgust a few seconds later.
Everyone's reactions to this are priceless, ranging from confusion to excitement to Leeron just being unimpressed.
Prior to this, Kamina's fruitless attempts to get Simon to combine with him. This includes throwing a boulder at him as he runs for his life.
The giant land battleship, Dai-Gurren, being literally a battleship on legs is funny enough. But then it has to be specially prepared to go on water. The special preparations consist of flippers and a paddle.
Let's not forget Dayakka's "I'VE GOT THE BEST WIFE IN THE UNIVERSE - SWING!!!"
After Yoko's rescues Nia from Adiane, Adiane is standing in the direct center of the Dai-Gurren.