A mysterious new restaurant has appeared in a Chicago suburb and it appears it is a secret spinoff from McDonald’s.

The restaurant, named CosMc’s, has been taking shape in the suburb of Bolingbrook.

Images on social media appear to show the new restaurant being constructed.

McDonald’s CEO Chris Kempczinski spoke about the idea in the burger chain’s second-quarter earnings call over the summer.

“CosMc’s is a small-format concept with all the DNA of McDonald’s but its own unique personality,” he said.

Further details about the restaurant have not been released, including an opening date, though Kempczinski reportedly indicated an early 2024 opening plan during his earlier remarks.

The chain apparently plans to test the restaurants in “a limited geography,” but more details were expected to be released in December.

The restaurant appeared to be based on a vintage McDonaldland mascot named CosMc, an alien character who appeared in ads in the late 1980s and early 1990s.

The move is the latest vintage revival for the Chicago-based fast food chain.