Son opens 21st birthday card and discovers his last three years have been a lieA British man was left stunned after opening a 21st birthday card from his parents - only to discover he'd been the butt of a family joke for the past three yearsView 2 Images The birthday boy was given an unexpected surprise on his 21st birthday (Image: Getty )A British man was left utterly gobsmacked after opening a 21st birthday card – only to discover he'd been the butt of a family joke for the last three years. Sarah Austin took to TikTok to share the rib-tickling moment from her son Charlie's milestone celebration, which has since become an internet sensation. The video kicks off with the birthday boy unwrapping a massive card from his parents, who prompt him to "read it out". "Happy 21st birthday, Charlie," he read aloud, unaware of the surprise that awaited him. As he delved back into the card, Charlie's expression changed dramatically: "I've had no black box for three years?