
What I have so far:
-If a Japanese character has blonde hair, the gaijin's blonde hair will be a different shade
-Even though English is his native language (usually) he will be unable to pronounce things properly and burst into random phrases such as "Oh my god!" and "Yes!"
-Though the show may have aliens, robots, monsters, or some other odd creature, the gaijin will ALWAYS be stranger than them
-They have a thing for roses