From adult happy meals to a mysterious restaurant, here's what's new at McDonald's

From a mysterious new restaurant, to more "flavorful" burgers, to an adult happy meal, McDonald's is making waves this December and beyond.

Here's a look at some of the happenings the Chicago-based chain is set to put into effect in the coming months:

Mysterious McDonald's restaurant in Chicago suburb

A mysterious new restaurant is under construction in the Chicago suburb of Bolingbrook, but it may be more familiar than you might think.

According to recently captured images showing the building's unveiled façade, it appears to be a spinoff from McDonald's, called CosMc's.

McDonald's did not immediately respond to NBC Chicago's requests for comment, but CNBC reported the company's CEO Chris Kempczinski spoke about the idea in the burger chain's second-quarter earnings call over the summer.

Here's what we know so far about the concept.

Tweaks to hamburgers

Slight changes to hamburgers that began taking effect at certain McDonald's restaurants earlier this year will soon be nationwide in an effort made by the chain to make their burgers "more flavorful than ever."

The changes were first initiated in West Coast restaurants earlier this year, officials said, before taking effect at other locations across the country on a rolling basis. In a statement to NBC Chicago, a spokesperson for McDonald's acknowledged that the changes will be in effect nationwide by early 2024.

The adjustments to the chain's burgers revolve around the way the buns, burger patties and cheese are cooked that McDonald's says will result in softer buns and gooier cheese.

“We found that small changes, like tweaking our process to get hotter, meltier cheese and adjusting our grill settings for a better sear, added up to a big difference in making our burgers more flavorful than ever,” said chef Chad Schafer, senior director of culinary innovation of McDonald’s USA.

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Other changes include white onions being added to patties while they sear on the grill, while adding more sauce to the chain's iconic Big Mac.

By 2024, customers all across the country will be able to "taste the difference" at all McDonald's locations.

Adult Happy Meals featuring McNugget Buddies

Beginning Dec. 11, "McNugget Buddies" — friendly collector's items in the shape of chicken nuggets, first introduced as part of Happy Meals more than 25 years ago — will be part of a new McDonald's adult meal called the "Kerwin Frost Box," the chain said.

The meal -- which comes with fries, a drink, choice of McNuggets or a Big Mac, and of course, a McNugget Buddy --is meant to help spark feelings of nostalgia.

McNugget Buddies were first introduced in 1988 as part of a Happy Meal collector's item. Newly-designed buddies will be part of each meal, the chain said.

Squishmallows

Squishmallows, one of the most sought after toys in the U.S., will be offered in Happy Meals later this year, according to the toy's creator, the company Jazwares.

Each Happy Meal will feature one of 24 exclusive Squishmallows, with participating McDonalds locations offering between 10 and 12 designs. Additionally, 14 of them will also include a themed digital playlist, which can be accessed via QR code and is meant to "capture the excitement and energy of each Squishmallow's personality."

While a specific date for the rollout hasn't been announced, a Jazwares spokesperson previously said Squishmallows will be available in Happy Meals nationwide in late 2023.

Holiday Pie is in, McCafé baked goods are out

McDonald's popular seasonal "Holiday Pie" has returned to select McDonald's locations for the holiday season.

Originally debuting in 1999, the seasonal dessert has sporadically popped back onto menus during the wintertime since then, including last year.

Similar to 2022, the holiday pie will not be available at all McDonald's, with the chain specifying that it can be found "at participating locations while supplies last."

Treats no longer available at McDonald's include items from the McCafé Bakery line-up, including the Apple Fritter, Blueberry Muffin and Cinnamon Roll, the chain announced earlier this year.

Phase out of self-service soda machines

The Chicago-based fast-food chain will be transitioning away from self-serve soda and beverage stations in dining rooms across the country, a spokesperson for the restaurant told NBC Chicago.

Instead, beverage stations will be "crew managed" -- which means customers will no longer be handed by employees a cup to fill up themselves.

The change, the spokesperson said, is meant to create a more consistent experience across all ordering points -- including McDonald's delivery, drive-thru, app or in-restaurant. It's expected to roll out over the next 10 years, as new restaurants are being built or as existing ones scheduled for remodeling.

By 2032, all self-serve beverage stations are expected to be phased out, the spokesperson added.