My Son the Salesman

We went to In and Out Burger this week.  We all got waters and we got one milkshake to share between us.  About half way through our meal, Nicholas starts saying, "Mom this is really yummy water.  Do you want some?  Do you want my water?"  I told him, "Thank you for offering, but I have my own water.  We both have waters so you can drink from your cup and I can drink from my cup."  He kept saying similar things until I told him I would love to have some of his water.  He passed it over to me and then announced, "Okay Mom.  I will have this cup now."  He then pulled over the milkshake cup and told us, "This is a good trade.  Yeah, this is a good trade.  You have your yummy water and I have this cup."  He had the sliest smile.  He really thought he had pulled one over on us.