What is a vipperloid?

Vipperloids are April Fools pranks Crypton has played on Vocaloid fans. They come out with UTAU voicebanks later. Teto's the most well known, so you probably won't need any guidance on her... I like Ruko, then there's Ritsu who sounds really cool... Sorry I'm not very helpful orz. But, uh, Ruko has a male and female voicebank and a male genderbend for some reason. I have a favourite cover with Ruko, "Rook," as he's called and Ritsu, that I'll embed here...

It's not the best quality but hnnngggghh.