Poison Cream

Isaac: “Dad, taste my ice cream.  It’s really good.”
Richard: “Okay.” [tastes ice cream].  “It is good.”
Isaac:  “Aha!  It’s poison ice cream!  Now you will die and I can do whatever I want.”
Richard: [feigns death].
Isaac: [grin changing to frown] “Oh no!  Mom!  [pause]  Um, Mom.  Taste my ice cream!”