Do you smell what the rock is cooking?

Yeah, mate, I reckon most people do. It's one of the most famous catchphrases in entertainment history. It comes from Dwayne 'The Rock' Johnson during his professional wrestling career in the WWE.

The "cooking" he's talking about isn't food. It's a metaphor for the beating he's about to deliver to his opponent. He was "cooking up a can of whoop-ass," as he'd often say. It was a rhetorical question directed at the crowd and his rival. He wasn't asking for an answer. He was telling them, in his incredibly charismatic way, that he was about to dominate the match. It's an absolute classic piece of trash talk from a legendary showman.