Know Your Meme cites the YouTube 'wtf boom'
“wtfboom” is a meme where a normal event gets interrupted by a loud voice screaming “ -” cut off by an extremely loud explosion, and a sinister laugh. It is commonly used as an element of surprise/interruption.
But a correspondent of Jay Nordlinger suggests earlier origins and a wider definition:
I see myself in 1975 at the beginning of my freshman year at university. I sit in a huge lecture hall with hundreds of others and am trying to keep up with whatever subject the professor way down in the front is blathering about. When my spiral notebook scribbling gets hopelessly behind, and I’ve completely lost the connection between what he is saying and what I am writing, I write for the first time a personal, profound, and profane note to myself, “wtf”, and re-engage at whatever the point the professor is now making, and start scribbling anew.