Preheat oven to 350℉, and grease a 9x13 baking pan.
Prepare brownie mix as directed on the box.
Pour brownies into greased 9x13 pan.
In a separate bowl, beat together eggs, cream cheese, butter, and vanilla.
Once smooth, slowly beat in peanut butter until combined.
Spoon peanut butter mixture over brownie batter. Don't spread it around, just kind of glop it on top!
Using a butter knife, swirl your peanut butter mixture into your brownies by slowly moving the knife back and forth, making sure to spread the mixture to each edge of the pan.