Pet Cactus

This cactus is almost like a pet. I've had it for eleven years, and it is fun to watch. It responds to environmental conditions by bending and twisting. Some days, the stems are straight, other days, they curve into a soft C shape. Sometimes, the stems almost form an S. Each stem (one is 35 inches long, the other 30 inches) does its own thing. I never know what it's going to do from day to day. On some days, it will be erect in the morning, and by late afternoon, it becomes curved, which is what occurred today when I took this photo.

I have never repotted this cactus. I water it once a month in the summer, and only once in winter, and since I haven't repotted it, I do provide it with a dose of cactus fertilizer in the spring. I'm not sure under which genus and species this cactus falls. It has many characteristics of the Opuntia subulata, but it has no spines, and as far as I know, there are no subulata species varieties without them.

I've always kept this cactus on the patio, so it does have some protection from temperature extremes. Last winter during the hard freeze, the stem on the right sustained damage to the growing tip, despite the protective Styrofoam cup placed on it. I wasn't sure if the one stem would survive, but in the spring, it produced a side shoot under the damaged area, and it is doing fine.

I suppose I should name this cactus, now that I've deemed it a pet. Any suggestions?