Not a cactus, but some sort of Asclepiadoideae like a Stapelia, Orbea, or Huernia. A flower would really help, but if I had to guess yours would be Stapelia gigantea or Stapelia grandiflora, but without a stinky flower this is just a guess. The flower on your little friend does not attract butterflies or bees, but they attract flies. So they smell like carrion🤮.

And their stink does attract flies. There are some neat pics out there of these type of plants that have fly larvae all over the flowers.

Back to your question, the longest piece is drooping because it could use more light. Slowly acclimate to stronger light. The long piece won’t revert back to being compact, but the new growth will be nice and sturdy once it receives stronger light.

Checked with the person I got this from and she said hers has purple flowers and yes they stink. So right on thank you so much!

Stapelia grandiflora has a big purplish burgundy flower.

Pic from Google images.

Gross pic I found of a fly laying larvae on a Stapelia flower, but it is kinda cool, at least imo🙂.

Lynn, if you've got a moment, take a gander at the flowers in the link - they're all succulent Asclepiads (now in the Apocynaceae), and rightfully called the orchids of the succulent world.

Really, Really Wild Flowers

There are some exceptions, but for the most part they smell like carrion (or worse), as Kara said - the better to get flies to pollinate them (itself a delightful process).

Even more gross.... a video of maggots hatching on a Stapelia flower

Edit, forgot the link:

https://vimeo.com/142793923

That video is crazy! Makes me happy to know that those baby flies died. I really hate flies, especially when one gets in the house.

The flowers on Stapliads are so complicated looking.

Looks like dragon fruit or close kin to one and they don't like the cold they turn to mush