These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Big Lipped Alligator Moment: The entire series is like this, but one incident stands out: during the fight in Z-block base, Beauty suddenly snapped and started going along with the series insanity, scaring the crap out of Heppokomaru. Eventually, when Bobobo and Don Patch finally got back into the screen, she went back to normal. This was never mentioned again, nor did it ever happen again.
Crack Pairing: Softon and Torpedo Girl even more crack with her Gender Bender transformation to the obviously masculine and not romantically interest OVER.
Absolutely EVERY song from the Japan-only PS2 game, Bobobo-bo Bo-bobo: Hajike Matsuri, in which you fight off enemies with your nose hair to the beat. Yes, it's a MUSIC GAME based on the Bobobo franchise and it rocks. Hearforyourself.
Ensemble Darkhorse: Pickles, who appears in the first chapter and is not fondly liked by Bobobo. He topped a Supporting Characters character poll.
Don Patch himself has topped all of the character popularity polls in Japan. The show referenced/parodied this.
He even got his own spinoff in Saikyo Jump called Fuwari! Don Patch.
And in Shinsetsu, we have Namero and Pokomi, the former an eternally stoic Deadpan Snarkerwho eventually becomes the newest emperor of the Neo Maruhage Empire, the latter being a lolita-bait, bubbly magical girl and Gasser/Heppokomaru's younger sister.
Arguably, Gasser is one as well; he topped second in the character popularity polls, despite him barely doing anything in the show.
Don't forget Rice. He's in about four episodes, and yet is insanely popular in the fandom.
We also have Jelly Jiggler. Originally appeared once in the beginning for a joke, but was liked so much he was given status as the Big Bad of a Story Arc, then pulled a Heel-Face Turn and became one of the show's main trio.
Gunkan/Captain Battleship, despite being shafted after his defeat, he's very much significant in the anime as he's promoted into more significance into Bigger Bad categories with his presence more apparent, added to the first opening's character roster and even the Big Bad of the Ps2 video game. Being voiced by Ryuzaburo Otomo/Paul St Peter helps.
Evil Is Cool: Battleship, OVER, Halekulani, J, Hanpen, Hydrate, etc....
Mainland Spain absolutely loves this series, possibly as much as Japan itself does. Two types of dubs (Spanish and Galician) exist there, even, and the Spanish one is commonly described as one of the best Spanish anime dubs ever made.
Moral Event Horizon - Bi-bibi is the one who caused the Hair Hunt in the Hair Kingdom because Bo-bobo was about to become the next king! Later in the battle, he used his true power, Kegari Shinken (Fist of Hair Hunt), to pluck out the Hair Balls out of Be-bebe, Bu-bubu, and Hatenko; and Bo-bobo engages him in a sword duel while protecting them. However, Bu-bubu's Hair Ball was broken when Bi-bibi stabs it and she dies. Then Bi-bibi took this opportunity and stabs Bo-bobo in the body, destroying the Hair Ball and killing him. But Bo-bobo came Back from the Dead thanks to Landmine Dandy replacing his Hair Ball with the Landmine Ball and defeats Bi-bibi with the help of the power from his allies. After Bi-bibi is defeated, he is spared because despite his evil ways, he's actually a good father to his daughters.
Nightmare Fuel: Giga, full stop. Especially when we find out just exactly where he gets his art pieces... He uses a clay voodoo doll of his opponent to mold their bodies- while they're clearly in pain- into abstract positions and shapes, then turns them to stone.
His Nightmare Face when he's on a high of overconfidence in his Super Form
Gunkan's life draining nosehair and the look he does beforehand isn't exactly welcoming
Byakko's surgery dolls and his overall Ax-Crazy-ness
Bobobo's Freak Out at seeing Gasser's Baby state, the camera is shaking and closing in & out does not help.
From the same episode, Don Patch being extremely calm despite often going on an instant rage almost always, hints that he might be angrier than usual
Sequelitis: Many fans on both sides of the pond find Shinsetsu Bobobo-bo Bo-bobo to have this for various reasons. Sadly, this plays out when Sawai was forced to end the manga after 73 chapters due to demand from Shonen Jump's staff and loss of interest from fans in general.