Bill the Scientist is exactly what he sounds like, a scientist. He aided in the creation of Blachu and is the one who accidentally infused Sonichus DNA with Cherry Cola making Blachu's fur black and red. His face is not shown in his debut, all we see is the back of his head.

This character appears again at a later date.

For Bill I'm thinking a monotone "I'm so done with this" depressed kind of voice would fit. The reason I'm looking for this kind of voice is because of how little he cares that he ruined what was supposed to be Sonichus clone by, as mentioned earlier, adding Cherry Cola to Sonichus DNA sample. If you have a different interpretation in mind however, by all means, go for it!