Unable to find a bicephalic actor (or at least, one who could learn his lines), the BBC resorted to Mark Wing-Davey, Zaphod on radio, and built him an animatronic head and an extra arm (mostly stuffed, but occasionally, when all hands needed to be seen to be working, the hand of someone behind him, sticking an extra arm out, as can be seen quite clearly in the Milliways sequence of Episode Five).
