When Rarity found out where Twilight was staying while in the human universe, she was not going to let her new friend sleep on a pile of dusty old books and, being the generous lady she is, invited her over to stay for the night. A slumber party if you will.
 
They did the usual thing; facials, watching movies, playing games and sharing gossip (though Rarity took the major role of that portion). Once they ran out of things to do, Rarity came up with an idea. She pulled out a few pieces of clothing that she had recently finished designing from her closet, bringing two new pieces from her lingerie line. Twi was of course a little reluctant, but after a bit of pleading from her friend, she agreed.
 
After they both changed into their new attire, Rarity led her to a mirror, showing how she looked, and she had to admit she liked what she saw. To save this moment, Rarity wanted to take a picture of the two of them together, and she was happy to take part. After setting up the camera for a timed shot, the two of them took a pose, holding hands as the moment was taken by the digital device. After that moment, they spent the night enjoying the feeling of their outfits, taking a few more pictures through the night. As they grew tired, they both flopped onto the bed, both of them snuggling up to their new found best friend. Perhaps something more. It was definitely The Best Sleepover.