Okay, we know from Changes  

So, could a powerful enough entity-- a strong wizard, for example-- with enough knowledge of the Nevernever use it to get into the living room of a romantic couple's house?  Six years together, no children, if that helps.

If so, what effect would this have on the power of the wizard?  Does this count as crossing a threshold, or has it successfully been bypassed?

Also, could you, say, let in Changelings who had not chosen yet-- and if they then chose to become Fey while in the house, would their power be reduced by being in a home uninvited?

As you can see... my players are a sneaky lot.