Can Invisalign Cause Hollow Cheeks?

I have yet to see a case where a patient ended up with hollow cheeks from Invisalign Treatment.  In fact, the opposite is usually true since Invisalign expands/broadens the arches -- it may result in fuller lips or cheeks.

Invisalign will usuall do the opposite. It expands or widens the arch for most patients, which is the most common problem we see. I suppose someone with a very broad upper arch with gaps between all their teeth who used Invisalign to close the gaps could see a slight narrowing of the arch but usually not enough to see with the naked eye.
PS: You Tube is not the place to go to get information about a specific treatment for yourself. One person's case will not be the same on you.

Although "never say never" and "anything is possible", often the results are the opposite.  Many times expansion of arches are necessary, which results in a more full face.
The treating Dr should be able to help educate you on what to expect.