The two katakana words/phrases that I found most interesting are フィレオフィッシュ(Filet O' Fish) ケンカ(Kenka).
When I saw the フィレオフィッシュ(Filet-O-Fish) on the Japanese McDonald's menu, I was surprised to see that the entire word was written in Katakana. Although it is a foriegn item and the word filet may be a foriegn word, Japanese already has a word for fish: さかな. Why wasn't the item called フィレオさかな? At first I thought it was because they didn't want to mix Katakana and Hiragana, but there are many items that mix the two on the menu. Now I believe that although the Japanese have a word for fish, the item "Filet-O-Fish" is a completely foriegn one, which, according to many Japanese textbooks, would require it to be written in Katakana.
The next word, ケンカ(Kenka), I found a little easier to understand. Katakana seems to be the alphabet used to write the names of places in Japanese even when the place name may be a Japanese word(kenka/けんか/ケンカ means fight). With that said, it seems only right that the restaurant's name is written in Katakana. I think this is done because the relatively straight and rigid lines in Katakana characters make the words, and in turn signs and advertisements, more noticable to readers.
What do you think?
-- ジョン