Going back to the album version of “MAD,” I don’t know how often performers (voice or puppeteer) have done triple duty with character voices, but as a personal opinion from listening more carefully, it actually sounds like Moss might have been doing all of the backing vocals (in all honesty I don’t know why I thought it was Cerf and Spinney; the high voice is too high up in range compared to Spinney’s regular female voices) and the other voice is too nasally to sound like Cerf (plus there are hints of the Green Alphabeat’s voice in “Count It Higher” and Jeffy from the haircut song).