"First things first," Jess said. "I think you ought to act more your size." She handed the shrink vial to Mary with both outstretched paws.
"Why can't you just grow up to me?" Mary protested.
"Because shrinking is more fun," Jess argued. "And neither cats nor rats are two feet tall."
Mary shrugged. She agreed with Jess on both accounts. Shrinking was pretty fun to experience, and the world was so much more interesting when you were smaller. Just looking around her room made her dizzy with awe. She wasn't sure how much of the vial she should take, though if it worked relatively, she would drink half of the vial to shrink to half her height.
Following that logic, she gulped down half the shrink vial and replaced the cap. While she watched it refill itself, she waited for the effects to happen. Sure enough, she started shrinking again. The box of vials became much bigger, and so did Jess. They were finally at eye-level again, at one foot tall.
"So now what? We could go exploring the house. Who knows what kind of interesting stuff I've overlooked every day?" You could hear Mary purr with excitement.
"But I want to try some more small animals," Jess suggested. "Exploring can wait."
"I know what will settle this," Mary thought. "A Shrink-Off"
"A what?" Jess said, confused.
"A Shrink-Off," Mary continued. "We'll each drink an amount of shrink potion without knowing how much the other drank, and whoever shrinks the most loses. The tallest person picks what we do next."
"Okay," Jess agreed. She loved the idea. "You're on."
"Great!" Mary said. She put down the shrink vial and scampered over to a box in her open closet. When she returned, she was carrying two plastic cups. They were quite large compared to her size, but wouldn't be difficult to drink from. "Leftover party supplies from my birthday," she explained. She set the cups down and poured half of the vial into both cups. "We don't want to shrink too much," she said. "So this way the smallest we can get is six inches."
The two picked up their cups, which they had to hold with both paws, and faced each other.
"We turn around, then drink at the count of three," Mary said. "Ready?"
Jess nodded, and they both turned away from each other.
"One, two, three!" Both girls brought the bulky cups to their small mouths and began lapping up liquid. Neither of them wanted to lose, but they also wanted to see a significant bit of shrinking, otherwise what was the point? Once they had decided their portions, they put the cups down and faced each other once again. Then they simply waited.