My Sister's Cat Like To Lay In Such Uncomfortable Positions

My sister's cat loves to nap, and take long, kitty siestas, and i always find her in some weird positions. I have always thought that she do it because it's cozy and warm for her. I don't have a scientific explanation, though. I'm not really sure that anyone does. The cats that we had for many years used to sleep sitting up with his back propped against the sofa or a pillow much of the time. I guess they are not much different than us. They just sleep in whatever position is the most comfortable for them.