Sergeant Major Zero is a Zeroid of the Terrahawks, and the leader of the Zeroids residing on Earth, with 100 under his command. As something of an indicator of this, he has his own personal tower to sit on while aboard the Terrahawk. His personality is that of a militaristic general, though he is shown to have a sense of humour and something of a cheeky side. He is voiced by Windsor Davies, in a similar role to his performance as Battery Sergeant Major 'Shut Up' Williams.

Zero is a hard worker when it calls for it, but will not tolerate silliness from any of his men. He has a sensitive side though. He was deeply saddened by the loss of 13 in the Terrahawks' first encounter with Zelda, and went to the trouble of organising a brief funeral for the dead Zeroid before returning to the Battlehawk. When another Zeroid questioned the idea of the funeral, since another 13 would be built, Zero gruffly responded with 'you know your trouble, 35? You've got no heart.' He has a good relationship with Captain Mary Falconer and nurses a soft spot for her, since she treats him with respect and regularly compliments him. Indeed, he was awestruck when she said he had behaved like a real man on one occasion. On the other hand, he has a somewhat tempestuous relationship with the Terrahawks' leader, Doctor 'Tiger' Ninestein. Ninestein's dislike of the Zeroids is regularly made clear, though he holds a special dislike for Zero. In response, Zero often goes out of his way to annoy Ninestein, such as when he achieved a higher score on Ninestein's favourite video game, replaced all the Zeroids' voices with his own when Ninestein ordered them standardised, and he has repeatedly broken the order of not thinking for himself. The latter has often proved itself to be useful however, as there have been several occasions when Zero's independent thinking has won the day. On every occasion where he has accompanied Ninestein into space, Zero has, without fail, bickered with Space Sergeant 101 over who is in command. The winner of this argument has never been decided upon.