What kind of aliens are involved in the Ancient Alien Theory?

Hello all,

I am doing a media makeup project on the aliens involved in the Ancient Alien Theory of human evolution. I am looking for opinions of what sort of aliens you think would have visited earth thousands of years ago?

I will use the opinions on this forum to create designs for my alien makeup project, which aliens do you think are most realistic and why?

We can go down the route of 'Prometheus' engineer ET's or 'Fire in the sky' dark grey aliens, or anything related.

Would the anatomy and physiology of an alien be similar to humans?

All opinions count!