In Dave Stevens' excellent comic The Rocketeer, the inventor of the rocket pack used by Cliff Secord is clearly Doc Savage, though he is never referred to by name and his face is always obscured. Monk and Ham also appear. In the sequel, Cliff's New York Adventure, Cliff works with a man named Jonas, who is clearly meant to be the Shadow, though he never dons his familiar outfit. One possible non-pulp crossover in this story that isn't often mentioned is that a cab driver named Moe (implicitly Moe "Shrevvy" Shrevnitz, one of the Shadow's agents) drives a taxi with the word "Sunshine" on one of its doors. The New York-based Sunshine Cab Company was featured in the 1978-1982 sitcom Taxi. This isn't the only reference bringing Taxi into the CU, but it's still pretty cool. The Rocketeer is one of Win's favorite comics, and the one that got him thinking of a larger Crossover Universe that had the members of the Wold Newton Family coexisting with other heroes. Dave Stevens died far too young, and he is missed by myself and many other fans of great writing and gorgeous art. He is also to be commended for everything he did for Bettie Page, upon whom Cliff's girlfriend was based and named after. (In the film adaptation of the comic, the inventor of the rocket pack was changed from Doc Savage to Howard Hughes, and Cliff's girlfriend was changed to an actress named Jenny Blake, among other changes.) IDW Publishing has done an admirable job of publishing new adventures of the Rocketeer, several of which have crossovers of their own.