The ambulance warning.
Rock makes the ambulance behind him part of his threat to Cena: the inaugural Undisputed Champion could leave WrestleMania in it. His attack reaches beyond the title to Cena’s reign and legacy.
Episode 16 · Final SmackDown before WrestleMania

Des Moines never gets the planned card. Standing in front of an ambulance, The Rock seizes the broadcast and turns the final SmackDown before WrestleMania into his own hostile address.
He challenges Skeletor’s authority, threatens John Cena and tears into LA Knight. Then he declares SmackDown canceled. The broadcast cuts.
Watch the full segmentThe Rock takes over the broadcast, threatens Cena and declares SmackDown canceled. 7:20.
Rock makes the ambulance behind him part of his threat to Cena: the inaugural Undisputed Champion could leave WrestleMania in it. His attack reaches beyond the title to Cena’s reign and legacy.
Rock calls himself the president of a world and insists Skeletor cannot control him. Management, the company and anyone standing in his way become targets.
He mocks Knight’s Megastar identity and rejects the idea that Night 2 should have a main event after his. In Rock’s eyes, WrestleMania belongs to him.