Actually, the katakana in this image says kachin which is just a sound effect, like doki doki. Now if you used translate.google.com to translate"だめ"（dame） then you would get useless, but that is incorrect. In many of the jdrama's and anime's that I watch dame is used as "don't". So, in this image Patrick is pulling out his sword and saying- "DON'T DO THAT THING THAT I DON'T WANT YOU TO DO!"
hmmm I remember something in an old nickelodeon magazine (before they stopped publishing) with a manga style cartoon featuring spongebob characters and a samurai Patrick. Was that Mark's drawing? If anyone knows please tell me *goes digging through old nick magazines to find it*