Image imported from derpibooru
Original Description:

Twilight Sparkle briskly walked up to the students with a big smile on her face. Coming to a stop in front of them and a rather gobsmacked Miss Cheerilee she addressed them.
“Hello! And welcome to the first ever class field trip to my castle! In specifically, this will be the first time I formally invite visitors into my laboratory to watch and learn how a lab works! This should be very educational and lots of fun!”
Miss Cheerilee opened and closed her mouth several times as she tried bring up the subject of the form-fitting, glistening black outfit. Before she could express the confusion raging her brain one of her students spoke up first.
“Uh Princess Twilight Sparkle. What is that you’re wearing?” The alicorn looked at the filly and smiled.
“That’s a good question!” The alicorn said. “When a pony is working in a laboratory you will often be dealing with dangerous materials, so it’s important to that you wear Personal Protective Equipment or PPE.” The light mauve mare looked down at her outfit. “This outfit protects me when I am working in the lab!”
Much to Cheerilee’s annoyance she found Featherweight busily snapping away photos at the apparently clueless, fetish, festooned princess. Attempting to get the situation under control the earth pony spoke.
“Well! I will say it is a very, well, um snug outfit! In fact it’s snug garment I’ve seen! Uh, is there a reason for it being so?”
Very pleased that ponies were so interested in lab safety Twilight does a happy little bounce which everypony notes with a bob of their heads. “Oh! Good question Cheerilee! Having an outfit that is snug like this means you don’t have loose sleeves or cuffs that can catch on items and accidentally pull them off a table!”
As Cheerilee parsed Twilight’s declaration another of her students spoke up. “Can anypony buy those outfits?”
The princess seemed to ponder the foal’s question before replying. “Well I will admit I didn’t find this particular outfit in any of my lab supply catalogs. My close assistant Page Turner apparently discovered them and got it for me. Why don’t we ask her!” Then she lead the very curious students and baffled teacher further into the castle.
A moment from my anthro MLP dreamscape.