True story...my folks vet came to the house when I was still a youngster living at home. I raised bunnies to sell as pets. I had a hutch with separate quarters for bucks/does/babies. One young male who my folks dubbed Bunnicula wound up getting out and hung out in the yard. He'd hide and jump out at you hence the name.
The vet came to the door and rang the bell and noted all the kittens that had come about from a female cat someone dropped off at my parents driveway sitting on the windowsill resting and did a double-take. There on the windowsill with the kittens was the young Bunnicula blending in with his feline friends.
How he got on the windowsill, I don't know. He had to have jumped from the wicker love seat out there up to the sill.
He was a humper too....My does were sort of humpy, but not to the extent of my bucks, so I don't have a lot by way of suggestions.....