Which one of these is not like the other ones?

Normally, my husband and I have two dogs, Oliver and Mandy. They are both Miniature Pincher's (Min Pins), Oliver was a wedding gift to me, and Mandy we adopted about 7 months after we were married, so she may not be all Min Pin, but she looks like one at least...ANY WHO: two dogs is plenty, we love being a two dog home. But what do we have now, three dogs, at least for a while.

You see, my mother, has 3 dogs, because she is plain crazy. She has two Sheltie's and one miniature Australian Shepard. She used to only have two, a male sheltie, Rex (un-neutered) and a female mini Aussie, Gabby (spade). My mom and step dad kept on going on and on about how Rex is such a beautiful sheltie and how they really wanted to breed him...they search all over for a female sheltie, asking the vet to set them up, and even putting a "personals" add in the paper, from Rex to perspective female shelties (it actually was pretty cute and funny) but had no luck finding him a girl friend. So my mother, who is brilliant at times, ran across a really pretty female puppy while shopping and looking around Dog Town while on a trip to Canton. In her infinite wisdom, she purchased this cutie little female sheltie, who is now known as Gracie (not spade). I imaging you see where this is going...my mom bought a girlfriend for Rex, well, I guess we can call her his wife since they are now together for life. So once she did this I asked, "So your going to breed Rex and Gracie to get that puppy from Rex you've been after?" "Yes," she replied simply. "And then you will have four dogs!" I exclaimed...."I guess so," she said. I'm telling you, at times I think she might be certifiable! To the point though, Gracie just went into her first heat (got her first period, my heart goes out to the girl) and the vet said its best to wait for her second heat to breed. So Rex has been kicked out for the next approximately three weeks, and the ever abiding daughter, who lives less than a mile away, of course agreed to let the heat-seeking-male stay at my "No Doggie Lovin" (meaning no lovin' among the dogs) home. This is how I ended up with three (unmatched) dogs in my house!