His first story for Timely Comics, a forerunner of Marvel Comics, was an eight-page backup feature starring a hero called the Secret Stamp in "Captain America Comics" #13 (April 1942); another, uncredited adventure of the Secret Stamp was published in "U.S.A. Comics" #7 (Feb. 1943). Other early work for the company included a story of the superhero the Terror and co-creating, with an unknown writer, the obscure Jekyll-and-Hyde-like feature "Gary Gaunt", both in "Mystic Comics" #9 (May 1942). After inking Al Avison on a Captain America story in "All Winners Comics" #5 (Summer 1942), Rico soon became one of the regular pencilers for that cornerstone hero of the publisher's, starting with the 16-page "The Mikado's Super Shell" in "Captain America Comics" #18 (Sept. 1942). By the following year, Rico was variously writing/drawing stories featuring such characters as the Human Torch, the Whizzer, the Destroyer, the Blonde Phantom, Venus, and the Young Allies.