Adult Gohan and Vegeta are walking CMOFs, especially Gohan with his dorky Great Saiyaman costume and poses, and Vegeta who comes up with funny quotes.
Goku and Gohan occasionally forget their own strength from time to time. Mild examples include the two trying to hold a cup normally and the cup shatters into a million pieces. But the biggest indication of this is when Goku gives his wife Chichi a reassuring pat on the back, only to send poor Chichi a distance of half a mile, destroying three walls of their house and annihilating a tree in the distance.
Funnier still: in the next scene, Chichi is only mildly irritated and has bandages on her head and her arm in a sling. Good thing she's Made of Iron, huh?
Mr. Popo appears in a window outside of the hospital where Goku is recovering after fighting Vegeta for the first time. Bulma sees him and reacts with perhaps the most hilarious expression in the franchise.
The Bulma/Mr. Popo exchange. Poor Bulma is absolutely terrified of Mr. Popo. She starts off whimpering ending in a terrified scream, whereas Mr. Popo does nothing more than exclaiming a very soft 'oh'. Queue somewhat an exchange of glances and continued zooming in on Mr. Popo's face. Hilarious. This scene can be carbon-copied straight into the abridged version!
Just about every scene with the Ginyu Force, but particularly their first appearance. After receiving their orders, they start stomping around like crazy to psych themselves up for battle — fairly mundane in and of itself, but Frieza's utter "What the f*ck?" expression is priceless.
In the Funimation dub, when Captain Ginyu, in Goku's body, shouts out, "Get ready... THE CAPTAIN'S COMING TO GET YOOOOOUUUUUU!!" before pausing with, "Wait...that doesn't sound right," and struggling to think of something else, leaving Gohan and Krillin to attack Ginyu, who shouts in surprise, "Hey! I haven't even started yet!"
Before that, when Goku and Ginyu are fighting, Ginyu pauses for a moment to "introduce himself properly", complete with one of his ridiculous poses. Which Goku immediately copies.
Goku: Like this? Ginyu: No, no, no, your other leg is raised. Goku: Huh... But, you know, this pose... It doesn't really do anything, does it? Ginyu: *fumes*
Dende shouting at Gohan and Krillin when they first awaken Porunga.
Frieza (as portrayed by Linda Young) has some pretty funny lines.
Frieza: (after killing Krillin) Pop goes the weasel, haha.
And this exchange with SS Goku:
Goku: They (the Saiyans) paid for their crimes. —-> Frieza: They paid for their crimes, really? I thought I blew them all up.
Don't forget some of Frieza's verydark comments after delivering the final blow to Vegeta and as he makes his dying words:
Frieza: Enough! Loud mouth! On and on like a broken record!, "He's just a corpse talking; I'll have to gag him to shut up." AND after Vegeta dies: "It's about time. Saiyans tend to linger like a bad odor."
Puar gets one toward the end of the Frieza saga. Puar, Oolong, Chichi, Yajirobe and Master Roshi are planning to go to Namek as backup. Oolong is packing his things and saying that they should reconsider, when Puar burst into tears, sobbing into a photo of Yamcha and ranting about how s/he's not going to take this anymore. S/he then pops up into the screen, suddenly wearing a martial artists' headband:
Puar: Let's KICK BOOTY!
The last appearance of the frog in Captain Ginyu's body near the end of the Frieza Saga is pretty funny too. Also, it's nice knowing that the frog (who hadn't done anyone any harm) not only made it to Earth, but survived the punishment Ginyu had put his body through before.
Near the end of Goku and Frieza's battle, Goku bitchslapping Frieza several times. And just before that, the face Frieza makes◊ after Goku slams his elbow into Frieza's skull.
Garlic Jr. Saga
It was probably only brought up in the dub but Marron insults Chi-Chi with "It's obvious your grandson (Gohan) isn't here now." Oh snap!
It's even funnier when you recall that Chi Chi was only 19 when she gave birth to Gohan, so Marron just called a woman in her mid-20's an old hag!
Vegeta wearing his "Bad Man" shirt in public. And getting relentlessly mocked by all of Goku's friends.
Vegeta: I'm a warrior, not a... a... a... a variety of flower!
Even Goku makes a quip about the pink shirt!
Vegeta: For starters, where in the world did you get that absurd looking outfit? Goku: It's the latest fashion on planet Yardrat, but I guess it does look a little strange. But at least it's not pink! Vegeta: Never mind! Who cares about your stupid clothes anyway!
While they're waiting for Goku to land, Trunks keeps looking over at Vegeta, (because he's his father that he's never met but he can't tell Vegeta because it might mess up the timeline). Vegeta assumes he's staring because of the shirt, and says "If you like it so much you can have it."
Screw the "Bad Man" shirt. Piccolo's Postboy outfit is where it's at. That he was wearing because Chichi forced him to take driving lessons. Yes.
Goku: *zooms past Piccolo's car* EAT MY DUST, PICCOLO!!!
Also, remember when Chichi could stand on the Nimbus? What changed?
Well, she managed to get Goku to help conceive two children, so she must have gotten quite a bit more dirty-minded...
Forget Goku, remember Piccolo's driving instructor? Talk about road rage!
After Goku's first attempt he asks how he did, his driving Instructor (a guy who's pushing on a hundred by the looks of it) tells him it'd be a million years before he gets his license. Goku freaks out and tells him he can't wait that long as he's got to train for the Androids. While he's talking they are in the middle of a Lake and start to sink and he continues talking as they go underwater!
Goku's reaction when Trunks tells him who is his mother is priceless. He actually falls down on the floor when Trunks spills the beans.
Goku: BULMA'S YOUR MOTHERRRR!!!!
Piccolo's (who can hear the conversation due to Namekians having ultra-sensitive ears) and Vegeta's reactions are quite amusing as well:
Piccolo: *barely avoids Face Faulting* Vegeta: *shocked* That man just pointed his finger and Kakarot fell down!
Vegeta's sarcastic explanation to Cell as to how he became so powerful so quickly:
Vegeta: "I do a lot of push-ups and sit-ups, and I drink plenty of juice."
The scene where Cell announces the Cell Games to Trunks.
Cell: I can't wait to see the look on their faces.*Trunks makes a horrified face* That's it, that's the look.
On that note, in the anime when Cell breaks into the news station to announce where he's holding the Cell Games, we have Master Roshi watching TV to find he's how interrupted by Cell breaking through the floor, and he changes the channel only for it to happen again, and again, and again, almost as if Cell is intentionally trolling him.
Chi-Chi: [crying] My sweet little Gohan's become a punker!
During the ten days before the Cell Games, Super Saiyan Goku is relaxing on the grass. Krillin wonders to himself about what an amazing fighter Goku has become. He sees a large rock lying nearby and deduces that if he throws it at Goku, the latter would sense it coming and catch/deflect it. It doesn't work.
As a bonus, it's a really cool Call Back to a similar scene in the very first saga of Dragon Ball, when Chichi tries a similar thing when she first meets Master Roshi.
"The Puzzle of General Tao", all of it. Goku locates two Dragon Balls inside a fortress run by Mercenary Tao and a mob boss. Goku comes in, acts all cheery at meeting Tao again and tells them that he wishes he had something to give in trade for the Dragon Balls. Then Tao, remembering how powerful Goku is, tells Goku that he can have the Dragon Balls if he can solve his puzzle game by dawn. He then takes off with Gokuís Dragon Balls and leaves while Gokuís distracted. By night Gokuís still working on the puzzle. The one henchman Tao and the others abandoned tries to help Goku with the remaining puzzle piece, but Goku tells him he doesnít want to cheat. Goku finally solves it in time, and the henchman honestly congratulates him! When the pair get confused about where everyone else went, Goku relaxes and says it doesnít matter. He just uses Instant Transmission. Tao and the mob boss are on the shore of a lake, congratulating themselves on the trick they pulled on Goku. When Goku shows up and shows Tao that he solved his puzzle. He then happily takes the other two Dragon Balls and flies off.
Cell has one funny moment where he scares the shit out of a reporter and his cameramen.
Anytime Cell and the media interact really. When he wants to announce his "Cell Games" tournament, he goes to Z TV and stops at the front desk. Everyone immediately recognizes him as the monster that's been going around eating people and start panicking, but he just calmly and politely asks which floor the news broadcast is on. The receptionist gives him the information, and he thanks her and just starts flying slowly upward, plowing his way through the ceiling and multiple TV studios on his way up.
Gohan Goes to High School is incredibly hilarious, from the fact that Gohan doesn't KNOW how to be normal to him FLYING up in the air in baseball to catch the ball and realizing everyone's looking at him to the fact that Videl is stalking him like crazy and how much like his father he is. The whole episode is a huge Crowning Moment of Funny. Special mention goes to the scene where Gohan flips out on people who misinterpret the Great Saiyaman and call it Great Singing man. "IT'S GREAT SAIYAMAN!"
Erasa: So, where do you live, anyway?
Gohan: The 439 Mountain Area. It's kind of remote...
Erasa: THE 439 MOUNTAIN AREA!? How in the world do you get here? That's got to be a four or five hour drive!
Gohan: Uhhh... that's just how dedicated I am to my education! (in thought) I can't believe I just said that!
When Gohan becomes the Great Saiyaman and fails to realize how ridiculous his costume is.
Piccolo: What is the meaning of those ridiculous clothes? Gohan: Ah, you just don't know style!
And later, Goku mocks it.
Later, as Gohan is on his way toward Roshi's island, he wonders to himself "Of all people, Piccolo. I mean, who is he to talk, he wears a turban for heaven's sake! And then there's those pointy little booties and who knows what thing is on his shoulders... Huh, come to think of it, I used to dress just like him."
Gohan doing his Saiyaman intro to a pair of random criminals, who promptly mock him saying his intro is stupid. Gohan gets pissed off and stomps a hole in the street telling them he worked really hard on that, so they both agree that it was really cool.
Chichi meets Videl. It goes about as well as you'd expect, with Chichi acusing Videl of being a hussy trying to steal her son and Videl trying to defend herself. It eventually regreeses into Chichi sticking her tounge out while Videl bares her teeth at her. But it speaks for itself really.
Then she finds out her family's rich, and suddenly she's a Shipper on Deck.
When (kid) Trunks reveals to Vegeta that he can turn Super Saiyan.
Vegeta: (stunned, watching Trunks zoom around) Did... I miss something? When was it that the pride of the Saiyan race was reduced to a child's plaything!? *orders Trunks to stop* Tell me, can the youngest child of Kakarot do this as well? Trunks: Yeah, we do it all the time! Vegeta: (in thought) Yes, naturally, it's a Super Saiyan bargain sale!
Another notable moment occurs after Vegeta learns that (kid) Trunks can go Super Saiyan.
Vegeta: If you can land a punch on my face, then I'll take you to the park for an hour. Trunks: Wow! You mean it? Okay! * Trunks attacks Vegeta and manages to land a hit on his face, then Vegeta reacts by punching Trunks in the face by accident* Trunks: *crying* You didn't say you were gonna hit back, Daaad... Vegeta: Well I never said I wouldn't hit you now did I, Trunks? Trunks: Noooo... but... Vegeta: Dry your tears! We're going to the park now! Trunks: *Trunks brightens up instantly" Yeah!
18's first time participating in a tournament:
Announcer: Number Eighteen. Uhh, is that your real name? Android 18: My father was a little dull.
During DBZ's World Tournament arc when Vegeta not only says his 8-year-old son will easily beat Hercule, but he then procededs to really rip into him. Right in front of Videl. So Gohan attempts the most awkward cover up of all time. See for yourself.
Piccolo: You know, I... don't think I'll ever get used to this...
From the DBZ World tournament arc, there is the re-enactment of the Cell Games, from the spoof Toei Video Ident ("*Waves and rocks!* This show is brought to you by waves and rocks...") to the speed racer speech that everyone was assigned.
Goku: Hehehehe! Well, it was ridiculous and untrue but it kept me entertained!
During the 25th Budokai, Videl has been keeping her ability to fly from her father. When he finally does witness her flying, he completely freaks out. A nearby Tournament official merely looks at him and says "So she can fly. What's the big deal?"
Another one from the tournament is the the Goten and Trunks' response to their ruse being revealed.
Announcer: Hey! The two of you can't fight together! You're disqualified! Do you hear me? Goten: Uh-uh. I think we're in trouble. Trunks: Me too. Should we go? Goten: Uh-huh. Trunks: Your tournament was stupid!
Goku: But Bulma's much prettier than Chichi! It's a compliment!
What makes this funnier is that fact that Goku, who has defeated Vegeta numerous times and frequently gives out Curb Stomp Battles, is cowering in fear of Vegeta and that Vegeta is temporarily taller than him, baring in mind that Vegeta's height has served as a bit of a gag.
"Gotenks Is Born", the whole damn episode. But it's these particularly hilarious gems from the episode that stick out the most:
Goten and Trunk performing the Fusion Dance incorrectly in their first attempt and the result is Gotenks becoming obese. The Z-Fighters facial reactions to the botched fusion are priceless.
Fat Gotenks then tries a "speed run" and only to move a few small steps forward before simply running in place and eventually running out of breath.
The manga version is arguably even more funny because you don't see how the fight actually happens. There's simply one panel of Gotenks storming off of Kami's Lookout, ignoring any advice from Piccolo, and on the next page he returns to the Kami's Lookout beaten, battered and bruised, simply stating:
The Fusion Dance is pretty ridiculous. What makes it hilarious is how cool and awesome Goku thinks it looks. Everyone else is just dumbfounded and Piccolo is horrified that he has to do it
Piccolo: There's no way you'd have gotten Vegeta to do this...
Becomes a brick joke as at the other end of the saga Goku tries to talk Vegeta into doing the fusion dance with him. Vegeta refuses.
Goku: But you haven't seen it yet! —->Vegeta: I saw the whole thing from the afterlife and there is no way you are making me do it!
During the fight between Gotenks and Super Buu, Gotenks is being awesome and showy and taking four hours to power up and call his attacks... until Piccolo, sweatdropping hard, points to Buu, who is obliviously reading a magazine and drinking a fruity soda. Gotenks is pissed and yells at him to get up and fight. Buu replies "Why should I?" and reluctantly does so, still enjoying his drink.
Super Buu's first reaction to finding out that he, Gotenks and Piccolo are all trapped in the Hyperbolic Time Chamber.
Buu: Huh?! But how do we eat candy?! Piccolo: We don't. There's none here! Buu: NONE?! NO ICE CREAM!? NO-NO CHOCOLATE!?!? Piccolo: *grinning* "Nothing. All gone. Buu: NOOOOOOOOOOOOOOOOOO!!!!!!!!!!
Most of the time Goku and Vegeta spend inside Buu counts. They bicker like an old married couple the entire time.
Goku: Open Sesame! Vegeta: *looks at Goku and grunts in iritation*
Dabura after he's dead is one of the most hilarious characters in the franchise: during his life he was the King of Demons, with all the evilness that implies. After dying, he's admitted into Heaven because "he would have enjoyed Hell". We later see him wandering around with Chichi, Videl, and Bulma acting like a complete Love Freak. Yes. The former King of Demons as a Love Freak!
This scene during the Buu saga, in which Buu falls for a girl and decides to make himself look pretty to her. He looks into a nearby magazine and sees a picture of a "pretty boy" and changes his face into the one from the magazine, while saying "Baby!" in an Elvis-esque voice.
Buu: Hello girl! You think Buu sexy? Girl: (terrified) Wha?! Yes, I... think you're very, very sexy! Buu: Yay, then give Buu smooch! *extends his lips* Girl: *screams in horror* Buu: Why you teasing Buu?! You play with Buu's feelings! *sees magazine* Hmm, what this? So Earth girls like boys look like this, huh? How Buu supposed to live up to body image in magazine!? Oh, Buu know! Buu rearranges his face to be pretty, girl reacts in horror. Buu: (Elvis-like voice) You girls don't know what you want!
The entirety of "Celebrations with Majin Buu" is pretty much an episode of True Life with Fat Buu. And it is hilarious.
Mr Buu (Good Buu) after Earth's memories of Majin Buu are erased being able to freely walk around. He tries to get ice cream and doesn't realize he needs money and winds up in a street fight and is told that if he wins, he gets to keep the money. The guy he's fighting just punches his stomach like crazy while Buu just happily says "Money, ice cream!" repeatedly until he finally notices he's being punched and lightly taps the guy into a wall.
Afterwards he goes back to the ice cream store and doesn't realize he gets change, but he insists they keep it because he wants ice cream.
Gohan and Videl fighting crime together. They show up at a jewelry store robbery in those ridiculous Saiyaman outfits and strike a pose more appropriate to the Ginyu Force. It's made even funnier by the fact that the bad guys surrender immediately because Majin Buu had just demonstrated himself to be Immune to Bullets. Gohan and Videl have no idea why the criminals are surrendering before they beat anyone up.
Goku looking after a dinosaur family whose about to have eggs. He ends up stopping two dinosaurs from fighting by picking them up and flying them to another part of the mountain and dropping them there and the dinosaurs' reactions are a Flat "What.".
After defeating Majin Buu, Goku takes a relaxing bath with Goten and Trunks. Then this happens.
Vegeta's reaction towards the whole event is priceless.