He also contributed scripts to Anderson and Christopher Burr's Supermacromation series Terrahawks, writing under various pseudonyms for all but one episode. All of these pseudonyms ended with the suffix "-stein" in imitation of the name of the leading character, Dr Tiger Ninestein. Barwick wrote 35 of the 39 episodes of Terrahawks; "The Midas Touch", which he co-wrote with Trevor Lansdowne, is the only episode for which he used his real name. With the completion of Terrahawks, Barwick went on to script the whole of Anderson's two-part stop-motion series Dick Spanner, P.I. (for which he was credited as "Harry Bolt").
