It all started with a business trip to America and a Grow Monster. All Harry wanted to do was bring something home to amuse his godson. It was close to St. Nicholas' Day and Teddy was going to be spending it with him this year while Andromeda went on a trip with some friends. Teddy dutifully set his shoes next to the front door of Harry's flat for Saint Nicholas to put presents in while he slept. The next morning he woke to a small pile of Weasley and Zonko products, as well as a small package that simply stated Grow Monster and showed a picture of a dinosaur.

Teddy looked at Harry, the gears of his four year old mind clearly turning. "Uncle Harry? Did Saint Nicholas give me one of Hagrid's presents?"

Harry grinned. "Nope, I actually left that one with a note for Saint Nicholas to put it in your shoe. I got it in America when I was there last month. I figured he wouldn't mind if I added to your presents." Harry took the package from the boy and started opening the stubborn plastic. "You put this thing in water and it becomes a lot bigger."

"Huh. Can we do it now?" Teddy had plastered himself to Harry's side to watch his godfather open the toy.

"Absolutely. I remember my cousin Dudley having these when we were kids. They always looked like fun, although I'm not really sure what my aunt did with them after they shrunk back down."

Teddy's eyes grew larger. "They shrink, too?"

"Yep. Once they dry out they go back to this size, so you can do it all over again."

The toy was a hit, with Teddy demanding that Harry magically dry the dinosaur out and wet it for almost an hour before Harry called a halt to it. Teddy complained, but they had to go to the Burrow for lunch. He scrambled to finish emptying his shoes of the wizarding toys and candy that he had barely looked at so he could get ready to feast at his unofficial grandparents' house.

Harry was happily ensconced on the couch in the living room next to Ginny when he heard the sound of a herd of elephants rushing into the room. "Uncle Harry! Uncle Harry! Do the magic again! Vic wants to see it." Teddy's hand shoved the dinosaur he'd gotten practically into Harry's nose.

Harry chuckled and pulled his arm from around Ginny to grasp the toy before it had a new home in his nostrils. "Alright, Teddy. I didn't realize you even brought this with you."

Teddy grinned. "It was in my pocket."

"What is it, Harry?"

"It's called a grow monster. It's not really magic. It's a muggle toy that you put in water and it absorbs the water and grows to an enormous size." Harry shrugged. "I may have sped up its absorption rate a tiny bit. It usually takes days but Teddy will be back with Andromeda by then, so-"

George held his hand out and asked Harry if he could see it. He handed it over to George without a thought. George turned it over and over and looked at it from all angles. He stood up from the chair and took Teddy's hand. "Let's go play with this thing, kid. I may have an idea."

Ginny groaned. "Oh, Harry, what did you do?"

The next Christmas, Weasleys' Wizarding Wheezes most popular toy line included a little wolf the size of a sickle that howled as it grew to the size of a book when water was applied, and a little bear that growled when it did the same, named the Teddy Bear.

My submission for the HP Mini-fest 2018 on LiveJournal.