Now is the time to add your fillings. Again, work quickly to keep the chocolate from seizing up too soon. Place each filling into the mold cavity on top of the layer of chocolate at the bottom. Make sure that the ingredients are small enough to fit in the mold without touching the sides or sticking too far above the tray, otherwise you won't get full coverage throughout the entire mold, and you'll end up with a mutant Invader (which is cool if that's your angle). Give it a few more taps and pokes so that the filling sinks into the center of the mold.
If you were to do a creme filling, you would take a "decorator's" brush and paint the floor and walls of the mold with tempered chocolate, chill them, repeat, and then fill the chocolate shells with your filling. I'd fill the legs and antennae with solid chocolate though, as these are the most fragile parts.