Maybe the normal kirby would be too "gay/friendly" for the american public... they try help his image with this... trying to avoid the "to childish look"

I'm tired of people trying to "Americanize" everything. They did this be changing words in the Harry Potter books, they did this with the MGS4 box art, and they've done this with plenty of other things. I feel like everyone thinks us Americans are a bunch of idiots.

I think the real question is why do they make him so happy in the Japanese art?

His home is repeatedly being invaded, his food stolen, his friends kidnapped or killed, and there are monsters roaming all over his land trying to kill him.  Why in the @#%% would anyone be happy in times like those?

I think the Japanese Kirby is on drugs.

You are indeed an insightful person.
I applaud you for catching on as far as you did.
You are worthy of the truth.
I was like you before, I've always thought that happy kirby was unnatural.
So I digged for the truth.
And the truth is much more vile than simple drugs .
Happy kirby is actually *dun* *dun* *dun* poring in disguise!
Yes, poring. In disguise. yes, gasp, I know how you feel.
You know how the wretched things just smile no matter how much you beat them.
It is all a part of their master plan of World Domination.
Dont worry though, I have discovered their next move.

Looks like any Mario picture, but please direct your attention to his skin tone.
Do you see it? It is pink, Mario does not have pink skin!

Now that I have given myself away, they will come for me.
But even if they dispose of me, my discoveries, my knowledge, my DREAM will live on with you.
Godspeed WoW, godspeed.

Because he's though!

hmmm I haven't noticed that until you have brought it up,
I guess they want to make Kirby look tough...but I don't see why since happy cheerful Kirby sells more

Props to the OP for picking up on that, I had never noticed. That is pretty funny. I think that it's because us 'macho' american men would never be caught dead purchasing something cute (unless it's for a wife/gf). Cute, smiling Kirby... stupid kiddy game. Angry, badass Kirby... I'll think about it.

Maybe it's a cultural thing.

In America the first Kirby advertisements always called him ONE TOUGH CREAM PUFF and I guess they stick with his hardass attitude over here. I've never noticed it, but that animated .gif is fucking awesome.

Kirby is like a Pink version of Samuel L Jackson.

"I have had it with these mutha f***in stars on this mutha f***ing game!"

I would assume it is because the Japanese are used to seeing animated characters that don't look like they're about to kill you everywhere, whereas Americans seem to prefer games where the main character's image screams "I will DESTROY YOU!" (Thus, you have the explanation for the American affinity to FPS.)