Would you let your son wear a skirt if he wants to? Why/why not?

How old is he? I noticed that toddlers are fond of using things of the opposite sex. My 3 year-old son does that too coz I think he's amazed with girls he sees on videos having long hair and nice dresses. I think it all started with Frozen. But I'm not too worried about it because we're orienting him well on how to behave like a boy. And he doesn't do it all the time so no fuzz, really.