I once saw what looked like a yellow lab puppy at the dog park. I asked how old he was. The folks said, "Four." I said, "He looks older than four months!" "No. Four years. He's a lab/chihuahua cross." (They didn't say "chibrador," fortunately.) Apparently it was the same story as the husky/retriever, two breeding dogs -- backyard breeding dogs -- whom the owners had let play together, assuming they were too different in size to breed. When the lab fell asleep, the chihuahua jumped her, and the lab barely even woke up. Fortunately, it wasn't the other way around, I know of one small dog who was impregnated by a rottweiler and didn't survive pregnancy.