I have found a few "quotes" which Miku uses to say. All of them are all made up words by himself. He's so creative, that little guy XD.

Kiteretsu: Could translate to a "very strange happening".
Nyappy: Happy (opposite is unnyappy which means unhappy).
Poppoo: Comes from hato (dove), and is the sound which doves make.
Tekesuta: Backwards of tasukete, which means "save me".
Tiramisu: Could translate to "have a nice day".