The Phantom Empire is a 1935 serial with Gene Autry as "The Singing Cowboy" who discovers an advanced underground civilization with robots and other high tech. Notable for being a mashup of the western, science-fiction and musical genres.
The serial was later edited down into a 70-minute feature, which was released as Radio Ranch (or, alternately, Men with Steel Faces) in 1940.
Do not mistake it for the 1988 low-budget film of the same name.
The Phantom Empire provides examples of the following tropes:
- Action Girl: Betsy Baxter, considering the time and the fact that she's maybe twelve years old. She rides, ropes, and fights. (In real life, the actress was herself an action girl as she was a popular trick rider.)
- Abnormal Ammo: The Muranian Thunder Guard carry swords. Early on, these are demonstrated to have spring-loaded grips, making them projectile swords. Later, flamethrower swords come into play.
- Ascended Fanboy: The Junior Thunder Riders Club start out as a perfectly reasonable cross between the Scouts and the Gene Autry Fan Club. After a situation forces them to adopt the motto "To the rescue!" they end up regularly pulling Autry's fat out of the fire.
- Cataclysm Climax: At the very end, the "disintegrating atom-smashing ray" winds up destroying the underground city and all its people.
- Cattle Punk
- Chekhov's Gun: Common for children's serials of the day, you can bet that if any new element is mentioned, it'll be used as a plot device within five minutes.
- Cliffhanger: At the end of every episode, to make sure kids came back the next week.
- The Coconut Effect: Since it has a radio Show Within a Show, it actually shows coconuts being used to make horse sounds. Being partly a Western, it no doubt had many traditional examples too.
- Crystal Spires and Togas: Murania has reached this point of development.
- Emergency Broadcast: Murania has civil defense sirens. They don't help.
- Enemy Mine: Gene Autry and Queen Tika near the end. It starts out as an alliance of convenient necessity, then moves on to honest mutual concern. It ends poorly for one of them.
- Forgotten Fallen Friend: Family, actually. Betsy and Frankie Baxter's father is shot in front of them in cold blood by Professor Beeson to frame Gene Autry for murder. They get over it remarkably quickly (on the order of seconds) and immediately set to proving Autry's innocence.
- Gas Mask Mooks: Any Muranian who goes topside. Terrestrial surface pressure is apparently too thin for them. Meanwhile, topsiders have no problem breathing in Murania.
- Heel–Face Turn: Queen Tika.
- Honor Before Reason: Gene Autry, once, in the last episode.
- Hyper-Competent Sidekick: Two for the price of one in the brother/sister team of Frankie and Betsy Baxter. Frankie is an electronic whiz, Betsy's a cowgirl, and neither one is at a loss in a tight spot. Gene Autry, on the other hand, regularly gets the crap beat out of him.
- Ice Queen: Queen Tika. She gets better, because Death Equals Redemption.
- Idiot Ball: Surprisingly averted. As silly as the plots get, the characters usually have a good reason for doing stupid things. Being a children's serial, they often state this reason aloud the instant someone looks at them oddly for their chosen plan.
- Ideal Hero: Gene Autry.
- Improbable Piloting Skills: Thoroughly averted, despite all the crises that happen in planes. When Autry and the Baxters get stuck in a plane with a flamed-out engine and a bailed-out pilot, it's all Autry can do to keep the plane steady.
- Literal Cliffhanger: Gene Autry suffers this early on.
- Mad Scientist: Mal, the Muranian who invents the "disintegrating atom-smashing ray." He's very proud of his weapon and the fact that it can destroy the universe.
- Opportunistic Bastard: Professor Beeson, the "villainous scientist" (their words). Not forward-looking enough to be The Chessmaster, he generally just does whatever's handy to screw whoever's between him and his dreams of vast piles of radium today.
- Race Against the Clock: Repeated. Gene Autry, as the Singing Cowboy, has a contract to be on the air every day at 2:00 PM. If he's not on the air, he's in breach and he and his friends will lose the ranch. This continues to be an issue throughout the serial, which means he has to make the schedule despite having to deal with the main plot.
- Red Shirt: Mr. Baxter.
- Save the Farm: Radio Ranch and Autry's airtime contract. All of Autry's friends rely on the Ranch for income, and this makes it a convenient target for the bad guys. Professor Beeson wants the Ranch gone so he can search for radium secretly. Queen Tika wants the Ranch gone so it stops attracting people to Thunder Valley and Murania's only connection to the topside.
- Schizo Tech: The entire serial aside, Murania demonstrates this. Robot labor, videophones, teleobservation technology akin to Star Trek viewscreens, atomic cruise missiles, and the royal Thunder Guard riding around on horses and wielding swords. They eventually get Ray Guns.
- The Starscream: High Chancellor Argo.
- Straight Man and Wise Guy: Pete and Oscar. Both are Plucky Comic Relief, but Pete is normally the more serious of the two.
- Thundering Herd: It's a Western. The Thunder Guard of Murania (legendarily known as the "Thunder Riders" to topsiders), the Junior Thunder Riders Club, Professor Beeson's gang, Muranian infantry, and pretty much anyone who happens to be chasing Gene Autry at any given point in time.
- Underground City: Murania.
- Well-Intentioned Extremist: Queen Tika. She's a stone cold ice queen, but everything she does is for the protection of her ancient civilization.
- Women Are Delicate: Thoroughly averted (in a 1935 children's serial!). Queen Tika and Betsy are both harder than goodly portions of the male cast.
- You Fool!: As a serial, this gets bandied around a lot. The last time it shows up is both tragic and patently obvious to modern audiences and of course it has to deal with the civilization-destroying disintegrator ray.