I've read that it's a stereotype in Japanese print or film for Chinese characters to use the copula "である" all the time. Is that supposed to make them should superficially bookish?

As a half-Japanese, half-Chinese Nisei who hasn't yet developed a native Japanese speaker's acute sense of what's おかしい or 変， I would like to know how such a copula sounds or what it could be compared to. And does anyone at all in Japan really use this copula in plain speech at all and if so, is there a reason they use it?

お願い致します。

That detail caught my attention while playing Guilty Gear with Jam.

You can see an example here.

http://oshiete1.goo.ne.jp/qa664789.html

Some Japanese answers for あるね・あるよ, ranging from direct translation of the Chinese 「了」 to coming from various actors or fictional works.

Ah thanks for the link albion, that Q&A page had some good answers.

And I used to play a lot of Guilty Gear when I was younger, I never noticed Jam talked like that! Her wheedly high-pitched "I just swallowed a flock of helium ballons" voice was already distinct enough.

有難うございました

The funniest explanation I read was pointing at a special kind of "easy Japanese" developed to be taught in Manchuria during the Japanese occupation. Apparently, ending sentences in ある was a feature of this language, with its meaning being both the Japanese verbs of existance and the Copula.
I have no idea though if there's any truth in that story.