Alright, here is a very strange way to use Barbie legs in a necklace! They are easy to pop out of the doll, but a little difficult to lay them properly to work with the piece and get the desired-end-product. Play with them a little, use chain, take a wood burner to them and make them do what you want them to, then you've have a necklace fit for a crazy person, like moi! :D

Fun, cool thing, you can change up the design because her knees click into place!

Step 1: What You Need.

Barbie legs!
Pliers
Jump rings
Chain(s)
Toggle closure
Wood Burner
Patience and imagination!

Step 2: Work Time!

Tear the Barbie apart, plan your necklace out. You will see, that while laying things out, you will prefer different layouts over others, but the real test is when you use the jump rings to put everything together.

Wood Burn or drill holes into the hip-like area of the barbie legs (top joint hole) and affix your wire to make it able to attach via jump rings or directly to your chosen chain.

Note - if you use wire, which I recommend to go through deep holes in the Barbie, just make sure to bend the wire so it won't scratch you during wear. :)

Step 3: Assemble

Now that you have your pieces chosen, you've got your design planned out, just work carefully through trial and error and bring all the pieces together. Specifically, with Barbie legs, you need to try the necklace on and see how it lays, maybe you want to add or remove links or change orientation around. Just know, you may not end up with your intended design intact.

Note: Count the links in the chain to match the opposite side because you want everything to be even.
Note: Sometimes, you don't need to use jump rings if you take the chain apart with pliers and use the intact chain links. :)

Step 4: Enjoy!

Now you have a crazy necklace that you are afraid to wear in public, but maybe the flesh tone kinda hides the fact that it seems like you are giving Barbie a piggy-back ride on your shoulders and her body is lost in your hair.

Another idea - paint the legs with designs to match your chain or centerpiece for more blending and contrast for fun! :) Use the rest of the Barbie for other projects, don't throw her parts away!