I decided to use copper plumbing parts because I had them on hand but this part could really be anything that has enough room to put the electronics in or on.
Drill holes in the end cap for the eyes and in the body for arms, belly button, satellite pole and wires. I use a hand drill and go slow, starting with a small bit and stepping up bit size incrementally.
I made the mouth with a Dremel and a cutoff wheel, but a hacksaw would work fine.
If you're feeling fancy and/or have them on hand finish the holes with aluminum grommets. On some I just used rivets for eyes on others it's a grommet + rivet mix.