ガリガリクン：
Gari-Gari Kun is the name of a crunchy Japanese popsicle. The name "gari-gari" derives from the sound it makes when bitten into. I've found Japanese onomatopoeia interpretation much more creative than those found in English. If Gari-Gari Kun had been introduced in an English speaking country the name may be far less inventive. English has only a few onomatopeia choices for a crunching sound, and each of those are used quite frequently. For example "crunch" in American snack foods appears in Cap'n Crunch, Crunch n Munch, Nestle Crunch, even health food such as Kashii GoLean Crunch to name only a few. One would be hard-pressed to find sound words as creative as Japanese in English.
ザトウクジラ："Zatou Kudzira", or humpback whale. I found this word in a Japanese tour book for Alaska. It's interesting that some animals' names were strictly 'loanwords' and others had Japanese versions. For instance humback whale is "zatou kudzira" but Beluga whale is simply "beruga". It's possible the beluga was discovered much later than humpbacks. Of course, it is likely that the book used katakana for each animal to give a standard appearance in the book, or it may be that humpback whale or most animals written in kanji are not as well known.
Katakana has many different applications; a fairly long history. My conclusion as to why there exists multiple textbook explanations on the matter is that katakana is over a thousand years old, originally used as a form of shorthand for Buddhist monks to transfer sacred texts. Since then, it's use has been changed multiple times due to different rulers in Japan, and most recently World War II. During the war, many modern loanwords were given new Japanese names. With all the change throughout history there is bound to be a degree of variance in katakana use.
