Blame the Marvel machine, but cinematic universes are now in vogue for studios. At best, they offer the promise of years and years of profits from fans who, once hooked, are guaranteed to flock to movie after movie. Star Wars is now on the cinematic universe track, and the once-unwieldy Transformers series is getting into the interconnected game, too. But perhaps the most interesting new cinematic universe development is Ghostbusters, whose franchise-kickstarting reboot hit theaters on July 15.

Ivan Reitman, the director of the 1984 original, even formed a new production company called Ghost Corps to oversee the rapid expansion of the ghostbusting franchise – with plans to create different films, TV shows, and merchandise derived from what was initially a goofy comedy. But the thing is, without knowing it, Ghostbusters has already been a cinematic universe trailblazer. Its characters and iconography have appeared in countless movies and TV shows, beyond simple winking nods and references. Here’s proof of some of the surprising examples of other things in the Ghostbusters cinematic universe.

Casper

It makes sense that a movie about friendly ghosts would at least require the assistance of one or more disgraced scientists whose job it is to bust said ghosts. But the 1995 big-screen adaptation of Casper starring Christina Ricci and Bill Pullman is the only movie we can think of in which an actual character from Ghostbusters, and not just Bill Murray showing up in Zombieland and talking about being a character in Ghostbusters, appears in another movie. It came in the form of a brief cameo by Dan Aykroyd as Ray Stantz, meant to be a punchline about the Ghostbusters’ general incompetence. But taken within the context of the movie it’s actually kind of surprising, considering the gigantic haunted mansion in Casper, known as Whipstaff Manor, is located in Friendship, Maine. Who knew the Ghostbusters made house-calls outside of the New York tri-state area?

They Live

Did these aliens in 'They Live' steal PKE meters from the Ghostbusters?

The Ghostbusters used their PKE (Psycho-Kinetic Energy) meters to hunt for pesky poltergeists, and the device made for an easy cue for the audience when one of them was about to get slimed. There’s no indication in the movie that it’s a multi-functional tool, so it was a delight when that very same PKE Meter (though it’s never specifically called that) shows up in director John Carpenter’s anti-capitalist cult classic They Live.

Instead of ghosts, this time the ghoulish aliens use them to track the likes of “Rowdy” Roddy Piper and Keith David’s freedom fighter characters, who infiltrate a local TV station to destroy the aliens’ brainwashing signal.

Doctor Who

This one is a bit of a cheat since there have been countless instances of character in movies simply referencing Ray Parker Jr.’s still catchy-as-hell Ghostbusters theme song. But it warms the cockles of a geek’s heart to think that the Doctor — the inter-dimensional being whose preferred means of conveyance is a shape-shifting police box — might have dropped in on Zuul trying to take over New York in 1984, saw the Ghostbusters handling it, and jumped through time and space elsewhere. Plus, the idea of a Ghostbusters crossover with the Tenth Doctor is a touch of nerd heaven.

Gremlins 2: The New Batch

No-Gizmos

Ghostbusters has to be the one 1980s movie blockbuster that filmmaker extraordinaire Steven Spielberg didn’t have a hands in, so it’s no surprise that he’d give a little tip of the hat to Ivan Reitman’s weird comedy horror movie in his company’s own comedy horror sequel. Gremlins 2 is bonkers on its own, but it’s even more so when one of the gremlins near the end of the film wears a t-shirt with a logo similar to the iconic No-Ghost symbol from Ghostbusters. Of course, Instead of the surprised ghost in the middle of the red circle with a slash through it, adorable Gizmo the mogwai is in its place.

Caddyshack

Deleted scenes count, right? This one boggles the mind because it means Ghostbusters is actually in the Caddyshack cinematic universe and vice versa. He isn’t identified by name, but the voice and general air of slovenly pride that Murray plays in the above scene cut from Ghostbusters is a spitting image of Carl Spackler, the bumbling groundskeeper from the golf comedy classic directed by Egon Spengler himself: Harold Ramis. That it came out four years before Ghostbusters only made it more fun in hindsight.

We just wish Rodney Dangerfield’s glorious loud-mouthed Caddyshack character Al Czervik made his way into Ghostbusters somehow, too.