The natives are apparently based on Asari's assistants, so their idiosyncracies might be based on drawing preferences (such as hiding faces behind objects). I don't think the kanji on their foreheads serve any purpose other than to distinguish them.
Parker's name and appearance come from the covers of the translations of Fred Saberhagen's Berserker series.
The legend of a carp becoming a dragon by leaping up a waterfall is apparently a Chinese allegory for a public official passing examinations. This raises interesting questions about the backstory of the universe, but it also gives an excuse for Belka to wear an extremely ‘80s biker suit.