Serra does NOT call Erk "Erky" ONCE in the entire game. I've read all of their conversations, support or otherwise, at least twice, and not once did a "y" get tacked on the end of Erk's name. Yet even in serious fics, there it is. "Erky".
Granted, it's not out of the question that Serra would do that-she is pretty silly and excessive a lot of the time, especially around Erk. But even so, it's pretty jarring to see it SO MUCH, as if it were a natural occurance.
This is just my 2 cents on the matter, though.