Let's get this out of the way. I used to really like Japanese Cartoons. But TV and american culture have become increasingly saturated by garbage meant only for brainless children and people who like whatever cartoon feces gets pooped out of Japan. Not only that, but every gutless animation studio had decided that they're all going to cash in on the fad and have created about a billion terrible shows that try their best to look like the worst of overseas animation.

One Piece is exactly why I got into anime in the first place. It's different, interesting, and created by people with imagination. One of my friends told me that Eichiro Oda, the artist behind the One Piece Manga created a notebook of goofy ideas that he wanted to see in a comic as a kid but never did. So, he just started putting them in his own comic, and hasn't run out yet, even after nearly a ten year stretch and 400+ chapters in the manga.

At this point, I don't remember what made me think to draw this image. It might have been subliminal since I saw Akira Toriyama draw a similar image for his Dr. Slump characters in one of the earlier collections. However, I think the characters personalities fit pretty well to the characters. Here's my thinking behind it, if you don't know the characters or can't piece it together yourself:

Luffy is the Straw Man. He wears a woven straw hat (Mugiwara Boshi) and is almost completely brainless.
Roronoa Zoro is the Tin Man. You could easily call Zoro heartless. He's killed about a hundred people in the comic, while the other characters generally don't kill any of the villians. Also, the Tin Man was the only one of the bunch that carries what could be considered a weapon, and since Zoro uses three katanas, I thought it would be fun to draw him with three axes.
Nami is Dorothy, and at first it was only because she was "the girl" and that was that. But looking at from her perspective, she's totally been taken out of her element and thrown into a crazy adventure with a bunch of wackos. That, and the Grand Line sea they're sailing is as strange and unpredictable as Oz. So that actually worked out better than I thought.
Sanji is Dorothy's loyal pooch, Toto. This makes me laugh. Sanji's a horny bastard who'll do damn near anything for a girl. So, he becomes Nami's lapdog in this picture.
My favorite character, Usopp, is the cowardly lion. I like this a lot because Usopp on the surface appears very cowardly, but he has the ability and intelligence to be as strong as any one of the crew. One of the major sub-plots of One Piece is about Usopp growing up to become a "brave warrior of the sea," not unlike the how the lion wanted to ask the Wizard for courage.

One Piece is great. That's about all I can say.