Seven, my husband has been going on all evening about the old guy. I didn't see it until your mouse drawing! We all had a good laugh, thanks.
The black circle is a look inside one of these, in her uterus.
The black you see is embryonic fluid. The Mexican man with the Sombrero is the fetus. Mom's pelvis is not visible at all, the white surrounding the black is simply denser tissue that is not fluid. Her bladder, viewed via ultrasound, would look the same, a big dark "hole" if it had urine in it. But no fetus would be present.