Yume is not lazy
http://i.imgur.com/gtCMGKTh.png
It was a pun on Japanese catgirls... they say nya instead of meow in Japan and if u watch an anime with a catgirl at some point, chances are that they will add extra "nya" into words and sentences.
The actual sentence is "Nan desu ka?", which is a polite term of "what? / what did you say?"... things like that. I made a pun by replacing nan with nyan (=^w^=)
