"How about the regular Centaur?" Luke was impressed with the equine portion - it looked like it belonged to a Clydesdale, with feathering over the massive hooves. The clerk nodded. "That's a nice one, and it just so happens it's sponsored, so it doesn't cost a thing."
That was a big plus! Luke frowned, though. "Sponsored? Does it have some sort of markings, signs or logos? I don't want to be a four-hooves sandwich sign."
"Nope! The horse part is classic Clyde, the kind everyone associates with beer wagons." The clerk hesitated, then added "You just have to take it off before sunrise tomorrow. You'll be a handsome centaur stallion, and I am sure you'll be very popular."
"What happens if I don't take it off?" Luke eyed the powerful-looking body with interest. The clerk sighed. "You go from centaur to total Clydesdale. It even includes transport to a stable where they use Clydes to pull wagons. So unless you want to spend the rest of your life on a show team and eating oats, I'd recommend taking it off as soon as you get home."
Luke thought about that and shrugged. "The party just lasts until midnight. I'll make sure to take it off as soon as I get home." However, the real issue was getting into the costume. It was full size, which meant he couldn't carry it. And after finding out he had to strip totally to slide into the front, it wasn't something he'd want to put on at the party anyway. So the clerk wrote up the order and had him sign it, and then helped him get in. He had to use a stepladder to step into the open neck and was surprised to find the cavity filled with warm goo. The muscular upper body was translucent and hung back until Luke slipped his arms into those of the costume. Then he gasped as the upper portion pulled closed around him and a larger head dropped over his own. For a panicked moment he couldn't breathe, but then he drew in an enormous breath. Relieved, he looked down and stared.
The upper body no longer looked like a costume part - he really did have massive muscles and a human upper body proportioned to the Clyde body. And he felt incredible! Powerful, massive, and... real. There was no sense of wearing a costume. He could feel his entire body, flick his tail, and move around on four equine legs as if he'd been born with them! He moved to a large mirror and was surprised to see a broad, thick-browed face that had a very horsey cast even though it was mostly human. And his voice! It was deep, and had a kind of whinnying quality to it. "This is amazing!"
The clerk led him out of the store, helping him maneuver through the aisles. The sun had already gone down, but the way to the party was all on main roads and well lit. Luke thanked the clerk and trotted off, anxious to show off his magnificent costume. He did not see or feel the mane that slowly grew out from his spine, or detect the very slow rise of the joint between hide and human skin. The clerk grinned as he watched Luke vanish into the night. Odds were good he wouldn't be getting that costume back.