1.) セイ- say (Used by レイザーラモン as an exclamatory.)
2.) ラーメン- Ramen (A Japanese noodle dish)
3.) フワフワ- fuwafuwa (Onomatopoeia; light and airy, the sound made when drunk, or sick)
4.) ネタ- Neta (A slang term for a hot topic in news or gossip)
“The limits of my language mean the limits of my world” -Ludwig Wittgenstein
This quote begins to grasp at the reason why katakana exists. As with any language, Japanese has limits. The concepts, emotions, and experiences we have, however, do not seem bound by these limits. As social creatures, then, it seems to logically follow that we would continue to strive for fewer and fewer limits on what we can effectively communicate.
An excellent example is how the meanings of words have changed to become ambiguous concepts rather than simple "things" over time. One such word (concept) is "happy". Originally, in ancient Greek, the word happy simply meant to be lucky, and why shouldn't it? Even today, the lucky are quite often happy as well. However, in this definition, "happy" is a very simple thing to explain. Over centuries, the word underwent subtle shift after subtle shift until modern times, where the word happy is a very subjective word. To some happiness is being in love (which in itself begs much further explanation), for others its being wealthy, for some its being near family, etc. However, these things themselves aren't happiness; these things are the most simple explanation for a universal experience that we all feel the need to express.
I posit, then, that the flexible and expansive use of katakana is another tool at enhancing the efficacy of the Japanese language. Some of the words are borrowed from other languages, presumably either because the Japanese speakers found the words more effective at making their point, or because the words work as well as it's Japanese counterpart, but is easier, quicker, or nicer to say. Other katakana words serve as Onomatopoeia, because sounds sometimes capture the essence of meaning much more effectively than the words to express the meaning can. (i.e., Imagine the sound commonly made from the back of the room when someone else does something that could be considered "crazy" or "insane".) Additionally, slang is sometimes expressed through katakana. As kanji and hiragana roots of words can lend their connotations to the words they build, it would not make sense for slang terms to be built from anything but katakana.
Effectively, it seems that the point of katakana is to expand the reaches of Japanese language, and gives the speakers of said language a domain to experiment with the language in. It seems a highly effective and beautiful effort at a language's attempt to meet the needs and expanses of the human imagination.
Sources: http://www.tofugu.com/2009/06/25/strange-katakana-words/
http://gakuranman.com/unusual-katakana-words/
Razor Ramon- Japanese comedian
