Jasper Sitwell graduated at the top of his class at S.H.I.E.L.D. Academy, with particularly high marks in airborne jump school and underwater maneuvers. When first introduced to S.H.I.E.L.D. Executive Director Nick Fury, the new agent's eager-beaver attitude meets initially with mock (and occasionally real) frustration from Fury and second-in-command Dum Dum Dugan, but Sitwell soon proves himself and earns his fellow agents' respect — albeit tinged with occasional humor aimed at his youthfulness and idealistic naïveté. Mentored by Fury himself and occasionally appointed interim director when Fury is on solo missions in the field, Sitwell later is assigned to Stark Industries as liaison between S.H.I.E.L.D. and that defense-industry contractor, which designs and manufactures much of S.H.I.E.L.D.'s ordnance and equipment. There he confronts costumed assassins and terrorists such as Grey Gargoyle, Spymaster (who shoots him and puts Sitwell in a coma for a time), and A.I.M., and even romances Whitney Frost, a one-time Stark paramour. Sitwell is eventually reassigned back to S.H.I.E.L.D., but continues to play a role in the affairs of Tony Stark from time to time. When Obadiah Stane takes over what was by then named Stark International, Fury sends Sitwell on an ultimately failed attempt to retrieve the Iron Man armors.