The dog looked at his human clothes that Luke was using to cover himself. "Oh, right. You didn't look more than ten, and pretty skinny at that. No way your stuff will fit me."
Luke made sure no one was around and shook out the T-shirt and jeans just to make sure. As he feared, the kid was a small ten year-old and Luke was at least an average-sized 18 year-old. Even though it was obvious they were not going to fit, the fog barked again. Annoyed, Luke held up the shirt. "WAY too small! If I try it on I'll just end up ripping your shirt." Then he grinned. "Which is fair, since you just shredded my stuff!" He yanked the boy's shirt down over his arms and had to really force his head through the neck. It was too tight around his throat for a minute, and Luke felt a little dizzy. Then the feeling passed - the shirt must have ripped, because it was suddenly a little loose on him. The dog barked, and Luke looked over and then gasped at what he saw. The Great Dane, the whole store was suddenly way bigger!
A check in a mirror across the aisle confirmed why - the boy who had barged into his dressing room was reflected back, wearing only a T-shirt. There wasn't much to show below, being as he was now only ten years old. "Oh, man!" Luke stared at himself. "This is freaky! Your clothes work like the dog suit!" The dog woofed and wagged his tail.
"Well, I'm already changed. I might as well get dressed." Luke put on the jeans and shoes, finding everything fit pretty well. He walked back and forth, surprised at how quickly he got used to his new size.