I just looked it up and Ross Bagdasarian did the voice of Alvin, Dave, and Simon. All of the Chipettes (and Theodore) were voiced by the same woman.
The secretary from Grease was the crazy babysitter.
This entire franchise is repulsive. And why the fuck are they the only talking animals? That always crept me out. No one seems to be disturbed by the fact that the Chipmunks somehow superevolved to become sentient.