Here's a cube with three things held captive in it. I used ZBrush to carve curved passages inside the cube and then snaked the things through them. Smaller cubes and spheres hold the things captive. There is enough clearance so that the three things are free to move around once the inside support material is removed.

I'm really not sure what to make of this thing, but it is interesting to maneuver the different pieces around.

I used ReplicatorG to prepare the file, a MakerBot Replicator2 with the Replicator 2 slicing defaults and the following settings with white MakerBot PLA to do the printing:

Infill = 10%
Layer Height = 0.200
Shells = 1
Feedrate = 40
Travel Feed = 55
Temperature = 220

I used a raft with full support.