Que buen sermón is a Spanish reaction phrase that spread through chats and short videos rather than from a confirmed film or show. Online, Spanish speakers use it the way English speakers use a sarcastic slow clap, aiming it at anyone who talks like they are giving a sermon. Its humour comes from praising the speech while clearly meaning the opposite. Because it needs no context beyond a long talk before it, the line works across group chats, gaming clips, reaction edits and everyday conversations where someone has gone on too long.