I have a 4.6 pound yorkie..and my mom has a 95 pound Boxer. The two see each other EVERY weekend; and have become best friends. When he isn't around she sleeps with one of his toys...adorable I know.
They play well together; the size it the issue...he is HUGE to her. But she uses that to her advantages...she rides on his head..or his back. She hangs onto his collar by her teeth and goes around the house. And he brings her toys when she is sitting on the couch and he isn't. It is the cutest thing in the world.