The 'What the Cinnamon Toast Fuck Is This' meme is a popular reaction image featuring a gritty, hyper-detailed, and visibly disturbed version of the Cinnamon Toast Crunch cereal mascot. First appearing on platforms like Reddit and Twitter around 2019, the image combines a childhood nostalgia icon with aggressive profanity to perfectly encapsulate a feeling of deep, bewildering disgust. It is most commonly used in response to bizarre social media posts, questionable life hacks, or 'cursed' images that defy logic. The meme's longevity stems from its visceral facial expression and the rhythmic, nonsensical nature of the phrase, making it a staple in the internet's arsenal of high-tier reaction memes.