Well, ummmm, they are not that different, cause DNA.

It appears that DNA is a structure of this universe (at least this galaxy)
Because space is such, DNA is such. The double helix. The amount of spirals per length...

So, aliens will be symmetrical across the middle-front, bipedal and have sight, sound, taste and touch

It appears that the "visible light" spectrum is actually pretty specific.
With only little difference into the IR or UV areas.

Now there will be some big differences. Things like having two sets of vocal cords