Doc Savage has a walk-on part in Dave Stevens’s The Rocketeer, where he is identified as the inventor of the rocket-pack which the strip’s hero Cliff Secord uses to fly. Two men looking very much like Monk and Ham, although never named as such, turn up at Cliff’s apartment, demanding the return of the purloined rocket-pack. Then, when he runs low on fuel, a bronze-skinned giant in jodhpurs and flying helmet comes to his rescue. Cliff’s pal Peevy assumes that the stranger is multimillionaire aviator Howard Hughes – but pulp fiction fans know better.
Doc can also be seen lurking in the shadows in the final panels of Superman
Annual #9 (part of DC’s 1997 retrotastic Pulp Heroes event); watching a newsreel of the Sub-Mariner fighting the Human Torch in Marvels #1; and, thinly disguised, as Doc Brass in Planetary #5.