According to Google the purple-eating McDonald's creature The Grimace was part of a special birthday meal that was being offered by McDonald's.

Source: https://nj1015.com/who-is-the-most-searched-celebrity-icon-in-nj-the-results-will-scare-you/

Much like James Blunt’s career and why Australia is in Eurovision, one of life’s great mysteries has been the often shunned McDonald’s character Grimace and what it is he’s exactly supposed to represent.

Source: https://www.bandt.com.au/maccas-goes-fully-retro-brings-back-purple-blob-grimace-for-latest-campaign/

The company also continues to gain traction from promotions, particularly ones aimed at kids such as its popular “Grimace Birthday Meal.”

Source: https://investorplace.com/2023/09/undervalued-growth-stocks-to-buy/

There’s an ABBA-inspired disco night Aug. 11 and Gen Z-friendly Grimace Shake Rave on Aug. 19, plus weekly karaoke sessions from 9 p.m. to 1 a.m. on Fridays and Saturdays.

Source: https://www.bostonherald.com/2023/08/10/how-to-spend-a-perfect-day-in-santa-cruz-based-on-your-travel-style/

The TikToks start with someone (often a teenager) wishing Grimace a happy birthday and taking a sip of the shake.

Source: https://adage.com/article/marketing-news-strategy/grimace-shake-tiktok-trend-and-how-mcdonalds-responding/2502096