interjection. Because on certain occasions, nyah-nyah has insufficient nyah.
Real citation: “(You just wait till Devanagari script becomes part of the ASCII code. Then I'll really party. No translate tools for you either! Nyah-nyah-diddly-dang-duddly-doo!)”
(Jan. 15, 2006, http://www.houseofleaves.com/forum/archive/index.php/t-4200.html)
Made-up citation: “Between doctor visits, I lost 31 pounds. I had two comments for my physician: ‘Nyah-nyah-diddly-dang-duddly-doo' and ‘In your medicinal face!’”