This created the technical infrastructure for rickrolling: a link promising something of interest — a game trailer, a news story, an image, almost anything — that led instead to the 1987 music video. The moment of click was the moment of vulnerability. The brief second of loading, the appearance of the familiar red-and-blue interface of a YouTube video, and then the sudden presence of Rick Astley in a double-breasted suit, pointing at the camera, with the first few notes of the song playing — this was the joke. The joke was not complex. It did not need to be.
The reason the joke worked specifically with this video, rather than with some other unexpected destination, is more interesting than it might appear. The video was of a real person. The song was a real song that many people knew, or half-knew, from a decade before. It was not offensive. It was not frightening. It was, in the terminology that internet culture subsequently developed, SFW — safe for work — which meant it could spread in contexts where genuinely offensive content could not. And it was, fundamentally, funny in the specific way that the unexpected and the incongruous are funny: you were promised a Grand Theft Auto trailer, and you got a cheerful white man from Lancashire dancing in a nightclub.
The joke also had a structural component that gave it longevity: being rickrolled was not a one-way experience. Being rickrolled created the impulse to rickroll someone else. The person who clicked the link became the person who sent the link, and the chain continued. This forward propagation was part of the mechanism that made the meme self-sustaining rather than dependent on continued promotion from a central source.