You can hollow out and carve the oranges a day ahead of time, as long as you keep them refrigerated.  Do not fill them with the fruit salad until shortly before serving (up to 2 hours before).Slice top off the navel orange.  Run a knife around its interior to hollow it out.  Scoop out the orange segments and reserve for filling.  Carve pumpkin face on one side of the orange. Repeat for other oranges.  Use a paper towel to gently soak up any remaining juice inside the oranges.  Dice up desired fruit, including the reserved orange segments and fill each cup.  Set the lid back on top and serve.
Source: Adapted from Disney Family Fun Magazine, October 2009