Place microwave popcorn in microwave. Cook in microwave according to directions.
Empty both bags into large bowl.
Mix corn syrup, brown sugar, butter and salt in a 2-quart saucepan. Stir constantly, bring to a boil over medium heat.
Boil 5 minutes without stirring. Remove from heat. Stir in vanilla, baking soda and several drops of electric green food coloring. Add as much green color as need to create the "ghoul" color needed; mix well together.
Pour caramel over popcorn in bowl. Stir to coat evenly or place popcorn in a paper bag and pour caramel over popcorn. Shake mixture to coat well.
If you prefer caramel popcorn that isn't so sticky, place caramel popcorn on greased baking sheets. Bake in 250 degree oven for 30-40 minutes.