My last dog, Gus, the Pit mix arrived about 3 months after we got talked into taking in a stray cat a friend found. I never really liked cats, but he was amusing, and once we got our two dogs to leave him alone, the big Lab Joe, in particular (He liked to "hunt" cats) everything was cool. Then we got Gus, and he and the cat, who was already about 13 pounds hit it off big time. I have tons of pics of them playing together. One of the things I never really understood was why the cat seemed to enjoy it when Gus would put his entire head in his mouth and suck on it. The cat, Orville, would pull his head out, shake it, and then pat on Gus's mouth with his foot until he did it again. A couple of years later, the cat was about 28 pounds, overweight, but he was a very big cat anyway, and was the "worst by far" patient at several vets over the years.
They slept together, and were very close. I used to see Joe, Gus and Orville all asleep together on the couch. One day though, it came to an end. Joe had to be put down after suffering a ton of little strokes and heart failure. Blackie, our other older dog was near the end too, and she never really liked to play at all, all she wanted to do was eat birds. One day, I was sitting there, reading the paper, and Gus and Orville were running around playing, as usual. All of a sudden, Gus is in the air, above my head, and I just manage to catch him (sort of, 75 pounds is a lot to catch) and keep him from landing on my head as he comes down. He's all shook up and his ears are all pinned back. Then I see that he's bleeding. The cat, just playing, had bitten him in the scrotum (Yikes!), and there was a hole in it! I did the peroxide thing and also used some newskin to "patch him up".
From that day on, and I don't really blame him, Gus was terrified of Orville, and never wanted him behind him. Orville used to torment him, and showed true bravery as he used to corner Gus and pop him on the face and "attack" him. Gus would snap at him at point blank range, and Orville wouldn't back down. Gus could have killed him in a second, but Orville wasn't scared. It got to the point if Gus heard Orville do his really loud "MEEEE-OWWW!", he would start shaking. Orville only did it when he was about to mess with poor Gus.
After Gus had to be put down at 14 due to cancer. Orville thought he was boss of the house, until King came. All 12 pounds of him, totally unafraid of Orville's hissing and attempts at intimidation. Orville found out just what it was like to be harrassed, being pulled out from under a bed and there wasn't anything he could do about it, having your food eaten, and all you can do is scream and hope someone carts King off before it's all gone. And all your terror tactics do is seem to amuse him. ANd every day, he got bigger and bigger, and there wasn't anything that he could do to scare him.
Orville finally, after a couple of months, figured out that King wasn't trying to kill or hurt him, he just was playing with him. Sadly, he had to be put down to either cancer or kidney failure at about 16 years old right after he figured it all out. We didn't get another cat, we didn't think it would be fair to it, as King is too "much" for a lot of dogs, let alone cats. Every so often, I get offered a kitten, and I sure am tempted.