The phrase combines two well known parts of internet culture. Hulk is Marvel's green superhero, famous for strength and smashing, while sus is shortened slang for suspicious that spread widely through the online game Among Us, where players accuse each other of being the impostor. Short mashup clips like this circulated on soundboards and in short form video edits, where a familiar character name plus a familiar slang word makes the joke clear without setup. It stays useful because the accusation is instantly understood, works out of context, and fits almost any suspicious moment.