Tiny Ron's character Lothar is made-up to look like Rondo Hatton who played similar characters in the "B" movies which inspired The Rocketeer. Ron can be seen out of makeup in a cameo as one of two Good Old Boys. He gapes as his companion marvels at the "Big gopher!"
Disney had a special mechanism built especially for this film. Called the "Shaky-cam", it was designed to be the exact opposite of the "Steady-cam", that is, to introduce vibrations into the picture. This was used in the scenes filmed inside the Zeppelin to give the impression of the power of the engines. When the movie went to video, the effect didn't transfer too well, and was therefore steadied.
Billy Campbell, who once studied commercial art, made sure to read the Dave Stevens graphic novel on which this film was based. He got the part after getting a haircut to make himself look identical to the character in the graphic novel.
The original inventor of the rocket pack was thirties pulp novel hero Doc Savage, the Man of Bronze, in the original graphic comic book by Dave Stevens. However, because licensing considerations, Disney did not seek permission from Conde Nast, the copyright holder of Doc Savage, and opted to substitute Doc Savage with the flamboyant billionaire Howard Hughes.
The plane flown by Cliff in the opening is the Gee Bee racer, specifically Model "Z" from 1931. It was built by the Granville Brothers Aircraft Company (brothers Zantford, Thomas, Robert, Mark, and Edward), hence the plane's initials "G.B." The R-1 was for a time the fastest land-plane in the world, essentially a cockpit, wings, and tail built around an 800 hp Pratt & Whitney Wasp engine. James Doolittle (who would lead the bombing raid over Tokyo in 1942) won the 1932 Thompson Trophy race flying a Gee Bee R-1 at a speed of 252.686 miles per hour.
In the original graphic novel, Cliff Secord's girlfriend is called Betty Page, not Jenny Blake. Dave Stevens (the creator of the comic novel) based the character "Betty Page" upon his real-life friend, 50's pin-up girl Bettie Page.
The reproduction of the Gee Bee racer flown by Cliff Secord is currently on display at the Museum Of Flight in Seattle, WA. The original Gee Bee this aircraft was based on was painted in the same color scheme as the one used in the movie, however the original was named the "City of Springfield" and was flown by pilot Lowell Bayles. Bayles flew barefoot, as he said it gave him a better feel of the rudder. He was killed flying this airplane while making a record speed attempt in December 1931.
When Eddie Valentine and his gang learn that Neville Sinclair is a Nazi, they quit working for him and join up with the FBI agents against the Nazi thugs hidden in the shadows. This reflects the attitude of real-life American gangsters during this era, in that they did not like fascism, particularly because Benito Mussolini persecuted the Sicilian Families back in the Old Country. Nor did any Jewish mobsters like Adolf Hitler. In fact, organized crime was one of the biggest allies the American government and law enforcement had when it came to rooting out Nazi spies and collaborators.
The trivia items below may give away important plot points.
The model that Cliff glides with to escape from Howard Hughes's warehouse resembled "The Spruce Goose", a plane built by Hughes which was so huge that many people doubted it would ever fly. This explains his "It does fly!" comment. At the time the film was made, Disney owned the Spruce Goose, and it's rumored that they placed this part in the film as a promotion for that attraction, which (apart from the Queen Mary) was the only money losing Disney attraction in the US.
One of Neville Sinclair's final lines is "I'll miss Hollywood" - and he does, as he crashes into the "land" portion of the "Hollywoodland" sign, which is now the "Hollywood" sign. It was built in 1923 to promote real estate property, in 1945 it was given to the city of Los Angeles. In 1949 the Hollywood Chamber of Commerce began a contract with the City of Los Angeles Parks Department to repair and rebuild the sign. The contract stipulated that "LAND" be removed to spell "Hollywood" and reflect the district, not the "Hollywoodland" housing development.