Marvel Family #85 (1953)

Wild apes have seemingly escaped from the zoo, prompting the NYPD to open fire wildly into a crowd. Billy Batson, Mary Batson and Freddy Freeman, watching nearby, call SHAZAM to become the Marvel Family, only to find that these apes are both intelligent and also civilized! The apes explain that they're from the Amazon Jungle and dress in top hats and tails with walking sticks, announcing themselves as diplomats of the Jungle Empire! The apes reveal they want to buy sophisticated machines from New York City and can pay in bags of gold coins, first for cars and appliances, but also hiring people to work in their developing gold-rich nation. The Marvel Family decide that helping out allies of democracy and freedom is a fine idea and start physically throwing cars from New York City to the Amazon Jungle via Mary Marvel throwing them and Captain Marvel Junior catching them. Meanwhile, Captain Marvel flies a big train-car full of people and the apes to the Amazon via the “Marvel Express.” Soon enough, the Jungle Empire embraces building Quonset huts and Captain Marvel meets their leader, King Zonga, and asks how they became so intelligent and all, but the ape village is soon attacked by crushing pythons! Junior knots the pythons together and they begin to help out around the Jungle Empire: keeping inexperienced driving apes from hitting each other, leaving food to burn on the stove and smoking cigars way too fast. Later, Captain Marvel finds that the human workers they've hired are passing out from deadly heat syncope, making Captain Marvel doubt their ability to continue, but King Zonga offers that they have made special food that will make them forget the heat of the jungle. King Zonga expresses a wish to use his portable radio transmitter, so the Marvel Family return Billy, Mary and Freddy, who start up a broadcast for him. However, when the kids eat the delicious jungle soup, they're also turned into apes! When they realize that this is some form of labor slavery going on, they're knocked out by King Zonga, who reveals that by feeding humans his “Primate Potion” they will turn into apes, and then, when exposed more, they lose the ability to speak and turn into spider monkeys. The Ape Kids are kicked out into a swamp next to a menacing crocodile! The Ape Kids figure out quickly how to use their prehensile tails to climb a tree and escape the snapping crocodiles. The Kids try to figure out why King Zonga is turning men into apes, but they soon find that they're losing their human sensibilities and losing their memories quickly. Once King Zonga is on his throne, thinking how he needs to talk about his master plan, necking down a bottle of “Homo Hormone” that turns him back into a human, the villainous Prof. Ira Gloot! Having discovered these two chemicals, he can now turn any ape into a human and vice-versa, having turned numerous Amazonian Natives into apes with his Primate Potion. Soon, he'll turn others into apes and become the Ape King of an Ape World! He then drinks his Primate Potion and returns to being King Zonga. The Ape Kids, having wandered back in, drink the Homo Hormone and return to being humans, then call SHAZAM and CAPTAIN MARVEL to become the Marvel Family again. Unfortunately, they find that was all the Homo Hormone in the bottle. The Marvel Family takes off for a nearby South American radio station, who refuse to believe that King Zonga can turn men into apes… until they turn into apes while laughing about it! This is because King Zonga is spraying it over the city like a crop-duster. They fly after the plane as it explodes, but that King Zonga already jumped out. They try to catch him, but he strips off his royal vestments and is immediately lost in a sea of apes. What's more, the apes who have lost their humanity now have decided to march against the humans together and the whole city is quickly lost to the Jungle Empire, founding the first Ape City. King Zonga soon shoves huge barrels of Primate Potion to spray over metropolitan areas all over South America to create his own Primate States! Captain Marvel gets the idea to gather up tons of feathers which work to start an artificial fog that forces the Ape Air Force to retreat back to their aerodrome. King Zonga orders his Ape Army to begin an all-out attack on the Marvel Family, who break down a riverbank, flooding the area and creating a field of mud that their military vehicles can't penetrate. After some time, the apes of Ape City admit that King Zonga left hours ago and they served as enough of a distraction. King Zonga sends up a giant rocket filled with Concentrated Primate Potion that will cover the planet. Together, the Marvel Family manufacture a gigantic air-pump that filters the Concentrated Primate Potion out of the Earth's atmosphere. They soon break down the walls of King Zonga's throne room and shove his radio on to him, then force him to drink Homo Hormone, turning back into Prof. Ira Gloot. Later, Billy, Mary and Freddy sign off on WHIZ-TV in monkey costumes for a party and say that Prof. Gloot went to prison.