What is what the fuck is up dennys?

Denny's is a large American diner chain known for its 24-hour availability (most locations) and its extensive menu offering classic diner fare. "What the fuck is up Denny's?" is a memetic phrase, highlighting the surprisingly popular and often unexpected online presence of the brand. Denny's social media, particularly Twitter, has become known for its humorous, self-aware, and sometimes irreverent posts engaging with internet culture and memes. The brand's unexpected online personality contrasts with the typical image of a traditional diner, contributing to its meme status and unexpectedly large following. Essentially, the phrase expresses surprise and amusement at Denny's unexpected and engaging online persona.