Blblbl has no single famous source, which is part of why it travels so well online. It is a generic vocal raspberry, the universal sound for mockery, boredom, and childish dismissal, and it has been reused on soundboards, in short-form videos, and in meme edits where a word would slow the joke down. Because anyone can make it and everyone recognises it instantly, it keeps appearing whenever creators want a quick, wordless way to say that something was silly, unimpressive, or not worth taking seriously.