Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This comic contrasts "good parenting" with "effective parenting" when it comes to discouraging a child from eating candy. In the first panel, labeled "Good Parenting," a bespectacled father gives his child a scientifically accurate explanation of tooth decay: oral bacteria consume sugar and excrete acid, which damages tooth enamel. In the second panel, labeled "Effective Parenting," the same father delivers the same information reframed in much cruder terms: "If you eat that candy bar, more bacteria will shit in your mouth."

The humor lies in the fact that both statements are technically accurate descriptions of the same biological process -- bacteria metabolizing sugar and producing acid as a waste product. The "effective" version simply uses viscerally disgusting language that a child would actually respond to. The comic satirizes the gap between what is pedagogically correct and what actually works with kids. A calm, educational explanation may be "good" parenting in theory, but the gross-out version is far more likely to make a child put down the candy bar. It also plays on the common parenting experience of discovering that rational explanations are no match for emotionally impactful (if vulgar) ones.