Genetically the cross is theoretically possible. The difference in size of the individuals, especially the reproductive organs creates a barrier that prevents crossing.
If the differences had been created via natural selection not artificial selection, a great Dane and Chihuahua would likely be listed as different species or subspecies for the same reasons.
Wait, let him cook. This might be the solution to idiots that want wolf dogs. Give them something that is technically a wolf dog, but too tiny to actually hurt anyone.
I have a wolf dog, and she is the sweetest, most loving dog I've ever had! Not an aggressive bone in her body, and she is about 50% pure FLOOF. I love her so much, and she is currently cuddled up on top of my feet as I sit here at my computer desk.