Question: A changeling's Change Appearance states:

> 
> You also can't appear as a creature of a different size than you, and your basic shape stays the same; if you’re bipedal, you can’t use this trait to become quadrupedal, for instance.
> 
> 
> 

But seeing that with a druid's Wild Shape can change you into a creature that is quadrupedal and a differerent size than yourself, does this mean that after that you can change into another quadrupedal creature of that same size?

Let's say you are a normal 2 legged medium changeling and you Wild Shape into a 4 legged large [saber-toothed tiger](https://www.dndbeyond.com/monsters/saber-toothed-tiger). Does that mean that you could use the Change Appearance feature of the changeling to change into another 4 legged walking large creature like a [dire wolf](https://www.dndbeyond.com/monsters/dire-wolf)? Could you also Change Appearance into a creature outside of the possible druid Wild Shapes? For example a creature with a higher CR?

Answer: 
It is at the GM's discretion.
=============================

The rules are somewhat unclear on this. While it is rather clear that *basic shape* was meant to refer to the changeling's, the part you cite somewhat contradicts this, by suggesting that a transformation quadruped -> quadruped works, especially so, since a changeling will by default never be a quadruped. 

I'd rule against the latter because RAI seems clear to me. If you rule otherwise, there is no reason to restrict the possibilities to wild shape forms so long as shape and size conform to the changeling's rules, such as one large quadruped to another one. 

**The CR is irrelevant when using change appearance**

However you decide, the changeling's trait does not change any mechanics, only the appearance. If you decide that quadrupeds can be interchanged, you can transform from a riding horse to an owlbear for example, but the statistics then are still those of the horse.
I would argue that there is no restriction from a Changeling using Shapechanger while in Wild Shape.
If the verbiage that is italicized above is relevant, then it would also prevent the druid from using a second use of Wild Shape while in a wild shape form, and it has already been clarified that this is possible:
[https://rpg.stackexchange.com/questions/96375/can-a-druid-wildshape-again-whilst-still-in-animal-form#:~:text=A%20druid%20can%20Wild%20Shape%20to%20a%20new%20form%20without%20reverting](https://rpg.stackexchange.com/questions/96375/can-a-druid-wildshape-again-whilst-still-in-animal-form#:%7E:text=A%20druid%20can%20Wild%20Shape%20to%20a%20new%20form%20without%20reverting).

Also, Keith Baker (who created Eberron) speaks about a Changeling Druid here: <http://keith-baker.com/faq-changelings/>