Liver alone--cheese mine!

Reader's　Digest 2月号の記事 "Laughter the Best Medicine" からの引用です。
Three male dogs are walking down the street when they see a beautiful female poodle. They all scramble to reach her first but end up arriving in front of her at the same time. Aware of her obvious effect on the suitors, she tells them, "The first one who uses the words liver and cheese together in an imaginative sentence can go out with me."
"I love lever and cheese!" the golden retriever blurts out.
"Oh, how childish," says the poodle.
The Labrador tries next. "Um. I hate liver and cheese?"
"My, my," says the poodle. "I guess it's hopeless."
She then turns to the last of the three dogs and says, "How about you, little guy?"
The Yorkie, tiny in stature but big in finesse, gives her a smile and sly wink, turns to the other dogs, and says, "Liver alone--cheese mine!"
最後の落ちが分かりましたか？
分からなかった人の為の説明は明日にでもしますが、私はこのジョークで "Honeymoon Salad" を思い出しました。