For 50 years, the hard-working teens (and dog) of Mystery, Inc. have been investigating the paranormal. What began as a single Hanna-Barbera cartoon series—Scooby Doo, Where Are You!—in the 1960s quickly morphed into a franchise with multiple spin-off shows, comic books, and a few questionable movies. That adds up to a lot of spooky stories, which have inspired fans to come up with their own creepy (or just plain crazed) tales about Scooby and the gang. Here are some of their best theories, including one that somehow connects to Patrick Stewart.

1. Scooby is a Soviet space dog.

For all the cases that Fred, Daphne, Velma, and Shaggy solved, they never got to the bottom of the show’s most enduring mystery: How and why does Scooby Doo talk? Some fans think he can’t really speak—that it’s just something his buddy Shaggy imagines while he’s high. But one Redditor has a much more complicated and compelling theory based on the show’s 1960s setting. At that time, America and the USSR were locked in the so-called “Space Race,” competing to see who could claim the first achievements in spaceflight. The Russians famously shot Yuri Gagarin into the stratosphere in 1961, but he wasn’t the first Soviet in space. Canine cosmonauts like Laika beat him by several years, and if the USSR was willing to put a dog in a rocket, who’s to say they didn’t experiment on him first?

According to this fan theory, Scooby is a runaway from the Soviets’ classified space dog program, designed to breed pups capable of operating satellites and understanding radio commands. Scooby was the best of the bunch, the rare test subject who could understand and imitate human speech. Naturally, one of the scientists got attached and defected with Scooby to the USA. When that scientist died, Scooby found a new family with a group of friendly teenagers. But the CIA never stopped searching for this Soviet wunderpup, which is why Mystery, Inc. is constantly traveling by van—and why the original show is called Scooby Doo, Where Are You!

2. The show takes place during an economic depression.

Warner Home Video

A classic Scooby-Doo mystery might take place at a theme park, museum, or mine—so long as it’s grimy and deserted. That’s a weird coincidence when you think about it: why are all these places so rundown? Well, that tends to happen when you’re weathering a financial collapse, and many clues indicate that’s just what’s happening in the world of Scooby-Doo. The towns he and his friends visit never seem to be doing well. No one has any money: Not the many scientists posing as monsters for cash, not the operators of every haunted attraction the gang investigates, and certainly not Shaggy and Scooby, who gorge on dog treats and lose their minds whenever they so much as smell a burger.

3. Mystery, Inc. is actually a cult.

Let’s break down the core members of the gang: You have Fred, the handsome and friendly frontman of the group. Then there’s Daphne, the fashionable and pretty one who mostly follows Fred around. Velma has the brains and Shaggy has full-blown conversations with a dog. When you really think about, doesn’t this all sound a bit like a cult? Fred would obviously be the cult leader, who recruits groupies like Daphne to obey his every command. Velma’s intelligence makes her a useful addition, and she could also be seeking acceptance from the “cool” kids. As for Shaggy, well, men who claim dogs can talk to them have a famously disturbing history—much like cult members.

4. They’re all draft dodgers.

Scooby Doo, Where Are You! premiered in 1969. Also happening that year? The Vietnam War. As able-bodied men (seemingly) over 18, Fred and Shaggy would both be eligible for the draft, which begs the obvious question: is Mystery, Inc. just a bunch of draft dodgers? The boys could be driving that van straight to Canada to avoid deployment, along with Fred’s fiancée Daphne and their antiwar activist friend Velma. Scooby’s stance on the war remains unclear, but he’s along for the ride.

5. Scooby Snacks alter your genes.

What if Scooby’s preferred treat is really a steroid capable of editing genetic code? It would explain why Scooby—and other members of his canine family, like Scrappy-Doo and Scooby-Dum—can talk, as well as their ability to perform “completely ridiculous stunts.” (Also, if Scrappy-Doo is on steroids, it would explain why he’s always trying to fight.) But what about its effect on humans? As far as we know, Shaggy is the only person who eats Scooby Snacks, and he seems to have a freakishly high metabolism, considering the mile-high sandwiches he eats and his super skinny frame.

6. Fred drives the Mystery Machine because the real owner is too high.

Whenever the gang piles into the Mystery Machine, there’s only one person behind the wheel: Fred. Mystery, Inc.’s de facto leader is constantly driving his friends from one haunted house to the next, which would imply that the Mystery Machine is his car. But why would a clean-shaven, preppy kid like Fred own a lime green van with flowers plastered over the doors? That car obviously belongs to a hippie, and in this group, that’s Shaggy. His hippie lifestyle, however, may be the reason Shaggy never drives. He’s either lost his license from driving under the influence, or Fred is worried he will, so someone else serves as his designated driver.

7. Shaggy is Captain America’s son.

This theory starts with small coincidences, like the fact that Norville “Shaggy” Rogers and Steve Rogers share a last name. Then it builds to something bigger when you factor in a detail from Captain America: The Winter Soldier. While out on a morning run, Sam Wilson (a.k.a. Falcon) claims that Steve can run 13 miles in half an hour, a rate that breaks down to 26 mph. Shaggy, meanwhile, frequently keeps pace with Scooby, a Great Dane. Those dogs run up to 30 mph. Ergo, Shaggy is Steve’s son.

8. Monsters really do exist in the Scooby-Doo universe.

Warner Home Video

Each time the gang catches a new “monster,” it always turns out to be a human in disguise, grumbling about how they “would’ve gotten away with it, if it weren’t for you meddling kids.” Monsters, the show tells us over and over again, are not real. But this Reddit theory poses an important question: If monsters don’t exist, why is there a business dedicated to catching the fake ones? The fact that Mystery, Inc. keeps getting calls implies that “supernatural fraud” is an entire category of crime, one that wouldn’t make sense or work if people didn’t believe in monsters. Everyone in the Scooby-Doo universe also seems to accept monsters as a normal and everyday occurrence, suggesting that monsters are real—the gang has just never caught one.

9. Shaggy and Scooby are actors.

When danger calls, Shaggy and Scooby tend to run the other way. But what if the group’s most cowardly members were actually actors pretending to be scared of ghosts, monsters, and other paranormal entities? According to this fan theory, Shaggy and Scooby are faking their over-the-top fear in order to draw the monsters out. By posing as easy targets, they know they’ll get spooked first, and thus make it easier for Mystery, Inc. to trap the ghost/witch/pirate. That’s why Fred always pairs Shaggy with Scooby when they split up to investigate, and it’s why after many years of investigating the supernatural, the two of them still don’t seem remotely used to it.

10. Green Room is just a gritty Scooby-Doo reboot.

The 2015 horror movie Green Room is about a band with a van that squares off against an evil old Nazi. The Scooby-Doo franchise is about a team (that was supposed to be a band) with a van that squares off against evil old men (who could also, theoretically, be Nazis). You do the math.