The most common Easter eggs are those kids go looking for on Easter Sunday. But to eagle-eyed fans, they’re the little inside references stuck in the most random places in movies, video games, television shows, and more.

And it turns out, Pixar loves Easter.

Variety reports that Pixar fans have long held to the theory that the animation studio’s films are connected, and “in fact take place in the same universe.” It’s called The Pixar Theory. Some of the company’s eggs are quite easy to spot: It’s common knowledge that the Pizza Planet truck has been in every Pixar movie, as has a reference to “A113” (A1-13 was the animation classroom at the California Institute of the Arts in the Character Animation Program). Variety says Boo’s toy collection in Monsters Inc. includes a Jesse doll from Toy Story 2, as well as a clownfish that looks a lot like Nemo from Finding Nemo.

Others are much harder to spot, however. Examples mentioned by Variety include one of the blue-colored cars from Cars being in the background of a fight scene in The Incredibles and the shadow of a dog who scares Remy in Ratatouille belonging to Doug, the talking dog from Up. The Today Show also mentions Easter eggs like “Riley from Inside Out showing up among a group of kids at an aquarium in Pixar’s latest, 2016’s Finding Dory,” and Sully’s likeness carved into a piece of wood in Brave.

Those are truly for the hardcore Pixar nut. If you grab your Pixar collection and start popping them in the DVD player to spot these, we wouldn’t blame you.