I explained to my cat before his surgery that if he didn't stay a little boy forever, his instincts would drive him to leave home and the life of constant play and treats and being allowed to sleep under the covers with me at night, and he would murder and pillage every creature in the neighborhood and would be an ecological disaster instead of my cute fuzzy boy.
I took his purrs and headbonks as consent. Years later he still seems happy with his lot.