Anytime Wily laughs. His sprite animation nails it.
Just about anything involving the Navi Customizer program Humor in 3-6. When installed, it allows MegaMan to make jokes to Lan when the L button is pressed.
MegaMan Battle Network
The oven is spitting fire due to a virus, so obviously the solution is to soak the entire thing in water.
Higsby's over-the-top pose when jacking-in NumberMan.
The ColorMan scenario really sums up the average intelligence of the adults on MMBN land. So WWW had just hijacked Den City's traffic lights, causing automated cars to crash and explode. One of their agents then announced a solution for the cars that costs a huge sum of 1,000,000 zenny, nevermind that the problem is with the traffic lights, not the cars themselves. And the generic masses just took the bait mindlessly.
Man: It's only 1,000,000 zenny this time! Cheap!
After Lan fixed the first traffic light, he has to talk some grown-ups out from being scammed:
Woman: Sell it to me! I'll pay you double! Triple!
Lan: Please! Calm down!
Woman: Hey, you're right! I don't even have a driver's license!
A scientist has taken a liking to Haruka:
Scientist: Who's that hot thang in the dress? She's my type!! What??? It's your mother? *gulp*
Wily: As soon as I press this button...Bye bye world! [Wily proceeds to prepare to push the button. This involves raising his arm in the air, finger poised, and twitching]
MegaMan Battle Network 2
Lan and co. went camping in Okuden, only to encounter Chaud at the entrance:
Lan: Chaud!? I thought you weren't coming? If you wanted to come, why didnt you just say so?
Ribitta:(at the Okuden campsite) My report for today is coming from a soccer camp! What do you mean they're not playing soccer here?
The way Speedy Dave expressed how two kids deleted QuickMan and screwing over his ecoterrorism act.
Dave: How could 2 kids beat me, future head of Gospel! (IQ 170!!)
What happens when you trade a style for the exact same one:
MegaMan: Trade complete! But what was the point of that?
When Lan is about to leave Netopia:
Netopian Airport Staff: I learned some new Electopian. Buzz off sucka!
The entire airplane rap-off is this, mainly due to how Capcom can get away with such an out-of-place rap.
MegaMan Battle Network 3
While Ms. Mari and Mayl are trapped in deadly bubbles during BubbleMan's scenario, Higsby showcases an expertise in martial arts:
Higsby: Step aside! Huh! I studied Yum-Fu in Yumland! (poses) HUH-YUUUUM!
Lan foiling Sunayama's hostage scheme is done by chucking Mega Man's PET at his head and knocking him out cold. What he says while doing it sells it:
Lan: Nowwwwww!! MegaMan, ATTACK!! *chucks PET*
When seeing that Dr. Wily has a statue of himself, Lan kicks it off of a nearby cliff while making a remark about Wily's bad sense of design.
The Yoka zoo computer area features an animal-based puzzle requiring logic. It starts with, for instance, using a cat-based Prog to remove a mouse-based virus... and then it quickly turnsintononsense.
The rabbit virus was so happy it exploded! [The rabbit program explodes]
Across the WWW Comps, MegaMan encounters the WWW Navis and their Operators again, who make use of the Pulse Transmission System to achieve Full Synchro, which is said to increase their fighting ability. The first opponent to demonstrate this is FlashMan, and despite all the fanfare... he only has a measly 500 HP.
MegaMan Battle Network 4
Translation errors are at its peak in this game, giving us a few gems:
Lan starts the day apparently trying to shove his mom in the oven:
Lan: You look upset. What's wrong?
Haruka: The microwave! It's broken, so I can't make breakfast...! I wonder if it caught a virus?
Lan: Just leave it to me! I'll jack you in to it!
Roll's reaction to MegaMan not wanting to battle her in the tournament?
"What a polite young man she was!"
Tensuke getting distresses by a malfunctioning TopMan during his scenario in Battle Network 4.
Lan: So why don't you just apologize? Netbattles are a lot funner if you enjoy them with friends.
Tensuke Whatever happens, I'm still a master top craftsman!
Tensuke I won't just apologize like it was nothing!
Duo's Anger Impact attack. He shoots down a ridiculous-looking angry face as an energy beam.
MegaMan Battle Network 5
Yai's "scared" face in Double Team DS. "HEEEEEELP!"
At the end of 5, Regal undergoes a Heel–Face Turn and gives a talk to the heroes like a calm father figure. What makes this scene amusing is that said speech is accompanied by his evil angry mugshot from his villainous days. This was fixed in the Double Team DS re-release, where he gets a new mugshot that reflects his reformed status more.
In the depths of the post-game dungeon, you can face DS versions of your version's exclusive bosses, which have the capability of using chip attacks or even Program Advances that you have favored throughout the game's progression. The game has a habit of making them move erratically before executing these attacks, so seeing the normally sluggish KnightMan suddenly blip across the battlefield is a sight to behold.
MegaMan Battle Network 6
A plumber's Navi loses his tool program, and Lan and MegaMan find it in their house's Toilet Comp, stuck to a Mettaur's head. Lan tells MegaMan to delete the virus, but MegaMan doesn't want to since the program looks harmless and doesn't want to touch it.
Yuika, Vic, and Ito split off from the WWW and plan to capture Iris. As they make their entry by bursting into Cyber Elementary, they mess up their introduction with each member giving the group a different name. The music stops for this moment and bickering follows.
An NPC lawyer in Green Town who becomes incensed upon learning about a case of dieting scam.