Speak of the World's Finest team on either Earths One or Two, and you are undoubtedly referring to Superman and Batman, who experienced several adventures side-by-side. Throw in Robin on some of those cases, and if you have a triumphant triad. Alas, Earth-S never had the same success with its Mightiest Mortal, Captain Marvel, and Dynamic Duo, Mister Scarlet and Pinky. Their first recorded meeting, in fact, was an accidental occurence that simply caused the pair to feel all the more deflated and dejected as the also-rans they ended up becoming in the golden age. Still, they at least had similar color schemes going for them which made them aesthetically pleasing in a pure fashion sense. Or maybe not!
If there were more meetings during the 1940s between these three crimson crusaders, these tales have been left unchronicled. Still, the fact that Mr. Scarlet at least started out in the relatively unknown burg of Gotham City (which Marvel hadn't heard of when asked if there was one on Earth-S by Earth-Two's Green Lantern) while Cap was the stalwart protector of Fawcett City, they rarely had occasion to bump into each other. And its not like Scarlet and Pinky could hop into their Red Rocket and jet over to see the Big Red Chesse, they hadn't the money even for a mode of transport aside from their legs and some handy lines to swing on between rooftops.
At least Cap had the courtesy to invite the duo to a commemoration bestowed upon the Marvel Family by a grateful public... although all present were captured in Suspendium and kept unaged and unmoving for decades to reappear in a modern era were they could teamup officially in the Squadron of Justice. And it definitely seemed like Fawcett was "REDdy" to have a pair of dynamic duos teamup in the their second "W" book. However, being as how their first, Whiz Comics, was home of Cap and Wow Comics was home of Scarlet and Pinky as well Mary after her initial debut... well they didn't have enough space for a monthly feature. More is the pity, for had they have been a World's Finest team, perhaps Billy could've gotten the crimson crusaders employment at his television station? Maybe Mary and Pinky could've explored deeper feelings between the two of them? Who knows???