Three words: Roller coaster rap. In both Japanese and English.
CHURROOOOOS!!!
"Chikuwa" in the Japanese version
Every Bo-bobo fusion will be dripping with this. This troper's favourite is BoboPatchJiggler's ridiculous voice, and absolutely everything about DenBo.
Basically the treatment of Don Patch, Jelly Jiggler, and Dengaku Man. At times, Bobobo as well.
The entire series is basically one big moment of funny.
"WE NEED, WE NEED GAS, WE NEED SOME GAS! LET'S GO!"
This early exchange:
Bo-Bobo: Don't call me 'Bub', because it's not my name. Call me Bo-Bobo, got it? Bo-Bobo!
Beauty: Okay... Bo-Bobo.
Bo-Bobo: CALL ME SIR, BOY!
Beauty: SIR YES SIR!
"IT'S HEALTHY AND DELICIOUS IT'S KELPKELPKELPKELPKELPKELPKELP YEEEEEEEEEEEEEEAAAAAAAAAAAAAAAH! KELPKELPKELPKELPKELPKELPKELPKELPKELPKELPKELPKELPKELPKELP YEEEEEEEEEAAAAAAAAAAH! KELPKELPKELPKELPKELPKELPKELPKELPKELP!"
When Captain Battleship is introduced to his Quirky Miniboss Squad, the Battleship Five Quartet, he notices that it has six members. So he opens a Trap Door and drops them out of his vessel. When an advisor calls him out on it, he opens a Trap Door under himself and falls as well.
Not in the original manga or the anime, but the PS2 game (which actually came before the anime and had a mostly different voice cast) features a scene (starts around 4:01) of Bo-bobo's head popping out of a door on Softon's crotch. Words can't describe just how bizarre and hilarious it is.