Here are some photos of how they were made. First I crocheted the skin of the monsters. I find it easiest to make the skin first, then make the armature to fit. Each monster was crocheted as four sections: the head/body, a trouser shaped section and two arms. After I'd made the skin, I placed the segments together, drew round them and made an armature from aluminium arnature wire and epoxy putty to fit the shape, leaving plenty of room for padding. I didn't add hands to the armature at this point so that I could still thread the arm wires through the skin. The feet have flange-nuts inside the epoxy putty to act as tie-downs.
I padded the armatures with polyester wadding, usually used in quilting, glued to the wire with Copydex (latex adhesive) and fixed in place with fabric strapping, usually used in first aid.
Then I 'dressed' the monsters in their skins adding extra stuffing where needed, then added hands made of epoxy putty and wire. I wrapped the wire fingers and the wire antenna in Copydex and yarn to make them thicker and rubbery. I threaded short lengths of french knitting onto the fingers and this grips to the rubbery surface to stop it sliding around. Then I finished sewing on the arms.
Now I just have to make the mouths then on to building the set - expect excessive use of LEDs, resistors and pretend alien technology...