General

Check out one of the pics in a recent slideshow (theonion.com/common-misconceptions-everybody-has-about-twins-1847202955/slides/24). Look at the banner pics on the homepage of this site.

What's even more interesting and funny to me is that it's a different pic with the same people. I've never seen them anywhere else.

This could be true, but I find it more likely that the two women in the photo are stock photo models, and both FF and the Onion bought two different photos of these women from the same shoot. As for why you haven’t seen them anywhere else, they could either be lost in the flood of stock images across the internet or they only ever did a few shoots (which would considerably lower the chances of you seeing them on any frequent basis).