Add the first 6 ingredients to a medium mixing bowl, whisk to combine. Lightly spray the inside of the slow cooker with nonstick cooking spray.
Add all the filling ingredients in a small mixing bowl and stir to coat banana pieces, set aside.
Cut bread slices into triangles (that's in half, just triangle-shaped). Place one layer of bread (6 triangles) on the bottom of the slow cooker, add 1/4 of the filling and repeat until there are 3 layers of bread. Add the remaining filling to the top.
Pour egg mixture over bread. Cover and cook on high 2 to 2-1/2 or low 4 hours, or until bread has soaked up the liquid.