I think most people have at some point in their lives and specialy in childhood. Well as a boy I had lots of older cousins who happened to be girls, so yeah lol you can imagine what that was like.
I remember them dressing me up when I was around 5-6 and the look on my mums face when she saw me, lol looking back it was bloody hilarious. Thankfully the internet and things such as Youtube did not exists back then or it would have been more embarrasing lol ahahah.
I don't think there is any harm in it, there just clothes really, our perceptions of clothing have changed over the centuries, Pink used to be a boys colour, Men used to wear tights and Roman men/boys wore tunics similar to dresses etc. These things are always changing.