The universe may be continuously expanding, but it still isn’t big enough for two companies selling cereal milk shakes.

Pastry chef Christina Tosi, who introduced her signature, trademarked Cereal Milk shakes when she opened her first Milk Bar bakery in the East Village in 2008, is tired of all the knock-offs — including Burger King’s latest promotion, the Lucky Charms shake.

Unveiled this week, the fast-food chain’s limited-time offer, on the heels of an earlier Froot Loops shake release, is a “mashup of our velvety vanilla-flavored soft serve and one of America’s classic breakfast cereals,” Burger King executive Alex Machado said in a statement.

The 740-calorie creation with soft serve, marshmallow cereal-flavored syrup, whipped cream and a handful of Lucky Charms unmistakably capitalizes on the taste Americans have for the milk that remains at the bottom of their cereal bowls. That same taste has made Tosi’s Cereal Milk — made with milk, cornflakes, brown sugar and a pinch of salt in liquid, soft-serve and shake forms — a cult favorite. 

Asked for comment on her corporate competitor's strategy, Tosi said, “Though I'm flattered at one level by the recent influx of copycatters, it should go without saying, you can never outdo an original!”

(Reviews of the Lucky Charms riff have been mixed on social media: "Ironically enough, Burger King's Lucky Charms milkshake is magically disgusting," one Twitter user opined. "TASTYYYYYY," said another.) 

Her message to Burger King and its ilk: “Inspiration is one thing. Stealing is another. Be brilliant, give yourself more credit than that. Come up with your own universe.”

Added Tosi, “You’ll always be welcome in ours."

Burger King offered no response to multiple requests for comment. 

The hamburger chain isn't the first company to ride Milk Bar's coattails this year: Ice cream manufacturer Ben & Jerry's introduced a "Cereal Flashback" line in March with a Cocoa Loco flavor, a Fruit Loot one and a Frozen Flakes variation.

Since 2008, Milk Bar has rolled out several twists on its Cereal Milk shake, blending in additions like coffee, hot fudge and truffles.

Correction: A previous version of this story incorrectly stated the location of Milk Bar's first bakery. Its first outpost is located in the East Village.