It's a meme, it's a prank often pulled that mimics the opening track of the TV series The Fresh Prince of Bel-Air (link to the KnowYourMeme article). It's a famous American show starring the then-young now-famous Will Smith.

A “Bel-Air” story typically begins with an engaging hook like a confession of personal drama or legal trouble and goes in-depth with the storytelling to entice the readers, but after a few paragraphs, the topic creator suddenly transitions into the lyrics of the Fresh Prince of Bel-Air.