For our lesson on John the Baptist, I demonstrated baptism for the kids with this mini Barbie and a clear bowl of water.  I demonstrated it a few times and asked if the kids had ever seen anyone get baptized.  Then I explained what baptism means as I was dunking Barbie.  It stuck with at least one kid, because my 6-year-old son explained the symbolism to my husband at the dinner table.  🙂