My toddler son always wants to play with my 'real' quadcopter multicopters. So, I thought making a toy multicopter would be a fun project that he'd enjoy playing with.
Solidworks files included for your remixing enjoyment.
1.16.14 update: increased center hole size of propellers and modified frame pegs for better snap & fit. Snap fits work well but are not "toddler rated"
1.16.14 update #2: added another option for the frame "REV2", which uses pins to attach the propellers to the frame. Use Acetone or your adhesive of choice to attach the pins to the frame and holds the props in place.
1.18.14 update: changed pin & frame configuration to work slightly better for press-fitting pin into frame. Depending upon the calibration of your printer you may or may not need to glue the pin into place, it depends upon how secure you want or need the pin to be.