Yeah mine are doing the same thing. It is like catfacing in tomatoes - the cooler temps at time of pollination. They are still fine to eat.

Dave

Haha that's cool! I've never seen a conjoined squash.

That's fairly common on my squash, especially late in the season. Yellow straightneck does seem to be especially prone, though, I had a lot of doubles last year, and only a couple on zucchini.

Sometimes there is even a leaf or stem running between the two. A few years back, I had a Tromboncino pair with a small vine running between them. I let that squash grow to full size, and picked it just before frost. Sitting on the dining room table, the attached vine bloomed for several weeks... watching it grow made the end of the growing season more bearable.

Mine are doing it right now

I occasionally have it happen.