You know, it probably would be faster to say "the entire series" and go to lunch earlier, but I guess we're all committed to this. And there is Episode 5.note (That is, the real Episode 5, not "Fanfic Mode.")
In Episode 2 - The way Luffy says "Ah yes, swords. Nature's knives." It just made this troper burst out in laughter at the absurdity of that statement.
Episode 3 - Shank sitting with his hand in the air, and suddenly, without it being commented on, a waffle simply materializes from his hand.
"I WON'T GO BACK TO PRISON, MY BUTTHOLE CAN'T TAKE THAT ABUSE!"
"If there's something you need to know about me, everything is made of rubber. And before you ask, yes. Yes, it is." What made it especially funny for this troper was that he was going to ask that exact same question until Luffy answered it in anticipation.
Also funny because the creator of the actual One Piece was once asked that as well, and he also answered in the affirmative, going so far as to have it be pointed out in the story itself.
"Sorry I punched you in the face and broke your daddy's statue! Think we can still be friends?"
Luffy's variation of a childhood insult had this troper in stitches.
I am rubber and you are fat! Don't you dare touch my hat! *Megaton Punch*
In episode four, Zoro gets finished lugging Luffy in a cage. Then Nami brings a key a Zoro yells about Nami having the F***-ing key. The hilarious part is that the next Sound Effect Bleep manages the fail to cover up the F-bomb, being placed right before it.
I DRAGGED HIS ASS TWO MILES, AND YOU HAD THE *BEEP* KEY THE WHOLE *BEEP* FUCKING TIME!?
(After viciously punching Morgan then knocking out Helmeppo in one hit)
Luffy: God that was unnecessarily violent!
A pirate mook trying to calm down the passengers on a cruise boat in the first ep
Mook: OH C'MON WHERE ARE YOU EVEN RUNNING TO?! ITS A BOAT!
Morgan's rant in episode 3.
Morgan: That's it, you pirate bastards! You're all going to die! I'm going to chop you limb from limb! You're going to have a little bit of the captain in you! You will die so badly you will be dead and then you will stay dead and - he's not listening, is he?
ALL OF EPISODE 5/14.5. Seriously, Purpleyes must be on some serious drugs. Not a lick of it makes sense yet it is the funniest part of the series. (So far.)
Particular parts to note: the cameo with the two Code Ment soldiers fighting over cheese, Death the Kid chasing down Lelouch and the entire party sequence (Lelouch is terrible a beer pong).
Zoro: "I'd suck a fart out of her ass."
Also worthy of note is Luffy's way of getting into Miss Kaya's estate.
Zoro: Why don't we just try the front door like Nami and Usopp?
Luffy: Because my idea's better. *zoom out, he's strapped to a rocket* NOW LIGHT THIS BITCH!!!
In episode 5, everything involving the dog was real. Purpleyes still kept everyone involved with talking to the dog in character.
Luffy (talking to the kid): Look, I have a rubber penis.
Nami (thinking): Ahhh... (that's why).
And before that...
Zoro: Hmm. This is not meant to be offensive to a group of people and their sexuality but you are gay.
Kid: I believe the term you looking for is effeminate—
Zoro: Shut up fa***t
Kid: I'LL HAVE YOU KNOW I'VE SLEPT WITH MOST OF THE WOMEN ON THIS ISLAND!
Luffy: Whatever heterof**.
The long rant where Kuro was a butler for three years.
Kuro: (to Django) Well it may not be a big deal for you; but outside your contact, the only people I've been able to hang out with are some weird annoying girl and a goddamned lamb-man! Let me repeat that: a god damned lamb-man! He's a ***ing man and a lamb. I have nothing in common with a person like that! What could I possibly talk to him about? "Oh yeah, how much do you sell your wool for in the market, I got jack shit because my dad didn't *** a sheep!"