Do you think underwear can be part of personal style?

Whenever fashion conversations begin, the topic is often jackets, shoes, watches, etc.

But recently I started wondering whether personal style extends to things nobody else sees. I came across a brand making novelty underwears, and it definitely made me realize that some people enjoy adding personality to every part of their wardrobe.

Do you think underwear is purely functional, or can it be an expression of personal style too?