Preheat the oven to 350°F (175°C).
In a large bowl, mix together the peanut butter, granulated sugar, egg, baking soda, and 1 teaspoon vanilla extract until smooth and well combined.
Press the dough evenly into a 12-inch round pizza pan lined with parchment paper, forming a cookie crust about 1/4 inch thick.
Bake the peanut butter cookie crust for 12 to 15 minutes, or until the edges are lightly golden.
Remove from the oven and let the cookie crust cool completely in the pan on a wire rack.
While the crust cools, prepare the frosting by beating together the softened cream cheese and unsalted butter in a medium bowl until smooth and creamy.
Gradually add the powdered sugar and 1/2 teaspoon vanilla extract to the cream cheese mixture and beat until fully combined and fluffy.
Once the cookie crust is completely cool, spread the cream cheese frosting evenly over the top of the cookie base.
Arrange the sliced strawberries, blueberries, kiwi, mandarin orange segments, and halved red grapes evenly over the frosting to create a colorful fruit topping.
Refrigerate the fruit pizza for at least 30 minutes before slicing and serving to allow the frosting to set.