Still not up for a proper post but I can probably manage a LTTBM so here goes.
When a work featuring non-human characters (alien, robot, talking animal, etc) neglects to replace human-specific language with more appropriate terms, that bugs me a bit. Why, exactly, is the alien who has never even seen a human before excusing his faults by saying: "I'm only human?" It doesn't make sense.
But what bugs me more is when such a work replaces species-agnostic terms with derivatives that specifically refer to the non-human nature of the speakers. The word "everybody" does not make any reference to species, so if you are an adult who is creepily obsessed with a certain children's cartoon, be very careful with your language or I might have to sever your leg.
Just to make things a little more complicated, all of my writing assumes the word "person" is a species-neutral term for any social sapient who might be present; mandraga are clearly not human but they'd be quite upset if a bigot declared they're not people. Not everyone shares this assessment (being as humans are the only people we know of IRL, it's not like the matter is easily settled by common usage), but I've been using it that way so long that seeing a non-human character replace "person" with a species-specific term just bugs me.