Kasper Larsson has been creating some great rigging tutorials through his site manoanim.com. One series, Maya Rigging Essentials covers creating a bipedal character form start to finish. The result of that course is a fully rigged Alien character.
Kasper has made the Alien Character rig free for download and free to use. The rig is pretty straight forward to use, but of you want to check out the features, Kasper has produced a short video that walks through all of the rig controls.
The Alien Character Rig includes bendy and stretchy limps and includes some nice smaller features, such as scalable eyes, IK / FK switching, stretchy 1-to-1 spine IK, automated pole vectors, and a bunch more.
If you are interested in learning how to rig characters like this, you should check out Kasper’s premium courses. Offered as an introduction to Maya Rigging, the essentials course is intended for anyone who wants to understand more about rigging and how things work under the hood.