All squash,pumpkins , courgettes etc fall into basically 4 families, they will pollinate within the family but not outside it.
Courgettes belong to the pepo family along with many winter squash and some pumpkins..
Butternuts belongs to the moschata family .
So you cannot pollinate a pepo with a moschata,or visa versa, but you can pollinate with anything from the moschata family. If you did cross with a different variety of moschata your fruit would be just like the mother plant but seeds from them would be different.
If you tell me what else you have growing I can tell you what family it belongs to.
It is possible that you have had male flowers and simply missed them, I have done that.
Crown Prince belongs to the maxima family as do the Hubbards, so Tricia your squash managed to do the deed themselves somehow. Maybe they got help from a passing bee who had been visiting in another neighbours patch,as they cannot cross with a courgette.They can cross with eath other though and many others.
I love the promiscuity of squash ::)
XX Jeannine