Piccolo is a long-running Dragon Ball character, famous as a stern mentor and former rival to Goku, which makes a casual modern greeting from him feel deliberately out of character. The phrase wsg my ninja borrows internet slang for what's up, my friend, and the clip circulates mainly as a short soundboard and meme audio rather than a line from a specific episode. Its appeal comes from that clash between old anime seriousness and current online humour, so creators keep reusing it for greetings, introductions and laid-back edits.