Here I come with the serious answer :^)!
To me role-play is invigorating. It's not invigorating for the reason stated above (i.e you can gender bend, change weight, etc), but rather because you get to unplug from your world and become lost in the character of a different human. It's a very powerful feeling. The idea that you can dictate someone else's life; their backstory, their actions, their convictions -- and in doing so, you lose grasp of your cares; your qualms, your anguish, your anxieties. It's a calming thing. Though role-play does get a bit more erratic, role-play tends to be relaxed and a time for nirvana. Personally, I use it as a means of therapy. I become glued to the immersion of unveiling the life of a character I created. Most of my characters taken after the Victorian Era style of speaking and likewise with their names, but their stories are different.
You see, each character I make represents a piece of whom I am. These 'throwaways'? I don't do that stuff. My characters will mostly, if not always, represent myself in some form. Their personalities and their bodies; be it a time I'd lived, a personality trait of mine, or something else. They will replicate and embody anything I want from my past, present, or something I hope upon myself in the future. This is what I love, most of all, about role-play, is the ability to use literary devices to convey ourselves and project an image of a totally different human to others. It helps us open up and helps us to communicate. This is also why I love theatre, it's an astonishing thing to experience on our computers let alone live on a stage before an audience of 400 people.