Beat butter and cream cheese at medium speed with an electric mixer until creamy. Gradually add sugar, beating until light and fluffy. Add eggs, 1 at a time, beating just until blended after each addition.
Combine flour and next 3 ingredients; gradually add to butter mixture, beating at low speed just until blended. Stir in bananas, pecans, and vanilla. Spoon evenly into 24 paper-lined muffin cups.
Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans, and cool completely on wire racks.