A few months ago I told Jack that if ever smoked a cigarette, his "wee wee" would fall off. It may have not been my proudest moment as a parent, but I figured it would be a decent placeholder until he would understand a conversation about addiction, disease, cancer, etc.
This week we were stuck at a red light in downtown. An older man was sitting outside the VFW smoking, and all of the sudden I hear Jack yell out his open window "Mister, you are making a baaaaaaaad choice".
I would say the message was effective.