I used this letter for teaching hereditary traits. The letter arrived in my classroom one day, along with plastic easter eggs filled with pompoms. I have enough eggs for each child. The students must look at the pompoms (which represent certain traits) in their eggs, highlight them in the chart, and then draw a picture of the alien, based on the traits that were in their eggs.
If you don't like the concept of aliens arriving in your classroom, you could edit the letter to be from talking bugs, or butterflies, or whatever fantasy you choose.