This is a line from the website realultimatepower.net, describing the fabled coolness of the ninja. Since I first heard this line, long ago at yet another e2 gathering, I have heard it repeated and repeated it myself a good many times. It seems to be a fairly funny line, although the reasons why are not immediatly obvious.
One of the first obvious reasons is that it is not very articulate, and it sounds like a hyper twelve year old going off, which is exactly what the writer wanted. But why does this line sound so accurately like something a twelve year old might write?
In my entire first year of Chinese, if I learned nothing else, I learned that there are separate styles of writing and speaking Chinese: an oral language and a written language. And once I realized that about Chinese, I realized that it was just as true of English. Most of the time that I read poorly written English, it is because someone is writing "spoken English" down. This is done by both poor writers and people without much experience writing, as in younger people.
The phrase "These guys are cool; and by cool, I mean totally sweet", is an example of a pattern that would probably be fairly commonly used in spoken English. Of course, it would usually be used for something less ludicrous than describing ninjas, and would have a more skillful use of adjectives, but other then that, the pattern itself sounds fairly normal. Imagine someone asks you about your drive home, answering : "The road was crowded...and I mean, it was packed!". In spoken language, pausing and then adding a stronger adjective would be an appropriate way to convey that the road was more than just normally crowded. There are many other applications of the same structure: "The weather was cold...it was totally freezing" or "That food in the refrigerator was moldy...it was totally gross". All of these sentences would sound fairly normal in spoken English.
In written English, however, they sound fairly stupid. First, the non-verbal cues of tone and gesture aren't present to convey the sense of meaning. For another thing, as long as someone is sitting down to write something, merely repeating a similiar adjective instead of actually trying to develop the point is a waste of space. However, the author of the Ninja webpage was obviously not trying to give an example of clear written prose. But they do give an example of how an inexperiences writer, a person with a ninja obsession and not much practice writing would write. The sentence is funny because it is a totally normal spoken English pattern appearing as written English, which is exactly how the supposed author of the page would write.