Add a tablespoon of unsweetened cocoa powder and about 1/4 cup of walnuts to make it a chunky monkey smoothie.
Skip the peanut butter and add 1/2 cup of oats (instead of 1/4 cup) to make banana oats smoothie.
Replace peanut butter with any other nut butter such as almond butter.
You can also replace milk with Greek yogurt.
TipUse a high-performance blender such as Blendtec or Vitamix when making smoothies with frozen fruits. If that is not an option, make sure to soak the dates in milk overnight or at least 20-30 minutes to soften it.