Yoga pants are ridiculously popular and comfy. I actually need a pair because trying to go to yoga in sweats or spandex is not the funnest thing in the world. With a pair made of 70% stretch bamboo, I might actually go to yoga more.
Soft pants are absolutely necessary for late night studying. They are presentable enough for late nights in the library and super comfortable - no more slumming it in PJs for late nights hitting the books.