A third limited run took place in the United Kingdom for one week, starting on August 28, 2024, celebrating McDonald's 50th anniversary in the country.

[1][2] Some McDonald's representatives described Grimace as an "embodiment of a milkshake or a taste bud", but his identity remains up to interpretation for many fans.

[9] It was then introduced to the United Kingdom and Ireland on August 28 as part of promotions celebrating McDonald's 50th anniversary in the country, available for one week until September 3.

[16] Steven Luna of Mashed.com said that, despite the shake being "pretty" and "magical-looking," it was disappointing and a "troubling tribute to a garrulous grape-colored goofball who deserves so much better".

[3] The video would then cut to a scene of the users finding themselves in unusual positions and in strange locations, or being discovered dead while covered in the drink.

[18] The videos are staged to look like a crime scene, with the shake splattered around, implying that Grimace is the assassin who is responsible for their transformation.

[1] McDonald's social media director Guillaume Huin said the Grimace Shake trend was unexpected and described it as "brilliant creativity, unfiltered fun, peak absurdist Gen Z humor".

"[23][24][‡ 4] The US launch of the Grimace Shake and its resulting publicity increased McDonald's next quarter sales by 10.3% in stores that had been open for at least a year.

[25] Many speculated that the Grimace Shake trend on TikTok was an intentional advertising strategy to raise awareness of the McDonald's brand for younger audiences; its indeterminate flavor and unnatural purple color have garnered significant attention on social media platforms.

[28] Fandom staff stated that the paid advertisement from McDonald's would last for the duration of the Grimace Shake promotion, and users would not be able to edit the page.