My aunts bunny thought it was a cat. Used the litter box, chased the other cats around, attacked your hand and played tag with you...
I wish I had pics of the dog and cat we used to have when I was kid. They'd wrestle, play tag, "talk" to each other. They were like siblings. When we brought the puppy home, he was so small (and our cat so huge) that he could walk under the cat. By the time he was 2, he could carry the cat around in his mouth. They got along from day one, the cat acted like his big brother, watched him and kept him out of trouble.
The worst part of when we had to put the cat down (he developed a brain tumor) was the months the dog spent looking for him. He'd go around the house checking out all his usual hiding spots and acting like he expected the cat to jump out and yell "Surprise" the whole time, then he'd sit down and give us the saddest and most pathetic looks I've ever seen. After a few weeks he'd even "cry" as he searched. He only gave up looking when we moved to a different house.