In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, cream butter and both sugars until light and fluffy. Add egg and vanilla and mix thoroughly, scraping down the sides of the bowl as often as is necessary.
Sift flour, baking soda, vanilla pudding and salt into bowl on top of wet ingredients and mix just until combined and all of the flour is incorporated.
Cover and refrigerate dough at least 3 hours and up to a day to allow the pudding to absorb into the cookie dough.
Remove cookie dough from fridge about 1 hour prior to baking to allow it to soften. Meanwhile, preheat oven to 350 degrees and line two baking sheets with parchment paper or spray with cooking spray.
Use a small ice cream scoop to place 12 cookies on each baking sheet. Flatten each cookie dough ball with your palm or the flat bottom of a drinking glass. Bake 8-10 minutes until lightly golden around the edges. Allow cookies to cool on the pan for a few minutes before transferring to a wire rack to cool completely.
Frost cookies with colored icing and make faces with assorted candies, marshmallows, googly eyes, etc...
One Last Thing
You can also make these cookies regular-sized if you like!