Seriously, I'd like to know.

not all of them were angry .....but i see your point tho alot are . it gives him a badass pink blob attitude thats why !

An angry Pissed off Pink Ball seems less feminist then a happy pink Ball... lol

 notice that the not angry ones were from a different country, all the US box arts had an angry kirby.

id assume they have some sort of research that shows angrier/meaner characters sell better in the US.  

Japanese = friendly
American/european = angry..

I never noticed it.

 Yeah, but the angry kirbys just look weird/stupid.  The normal kirbys look better, despite being more effeminate in the eyes of some.

All the american ones were and none of the Japanese ones were...

Also, when is the next real Kirby coming out? Is Kirby Wii still in the works?

I give this a GIGANTIC LOL, that is frikkin hilarious. At least they don't have him with beard stubble and a gun with an american flag behind him in american box art.

It's honestly a demographic thing (I would assume). Americans don't want a happy go lucky oblivious pink hero. They want an angry brooding bad ass....pink hero....