The video begins. The first few frames do not immediately betray the deception — the 1987 video opens with a fade-in that takes a second to resolve into recognizable content. The moment of recognition — that what you are watching is not what you expected — is the moment of the joke. This is the classic structure of the bait and switch: the bait is the expectation created by the link, the switch is the content that appears when the link is clicked.
What makes this work better with “Never Gonna Give You Up” than with, say, a random video of a person falling is a series of specific qualities of the song and video. First, the song is recognizable to a very large percentage of the population that encountered it — across different age groups, different countries, different cultural contexts. Recognition is part of what makes the joke land: the person being pranked needs to understand that they have been pranked, which requires knowing what they are being shown. Second, the song is genuinely pleasant — it is not unpleasant to be watching the video, once the initial surprise has passed. The emotional valence of the prank is light: mild surprise, mild amusement, the specific pleasure of having been caught out by something low-stakes. Third, and perhaps most importantly, the video has the quality of extreme 1987-ness that makes it unmistakably a period artifact. This quality is part of the joke: you were promised something current and relevant, and you got 1987. The temporal displacement is part of the humor.