It was an ordinary Saturday afternoon, and two best friends, Timmy and Ethan were hanging out in Ethan's room. As they laughed and joked, Ethan's eyes fell on a package lying in a corner - baby diapers his mom bought for his new baby brother. An idea struck him.

"Hey Timmy," he smirked, holding up a diaper, "Ever wondered what it feels like to be a baby again?" Timmy scoffed, rolling his eyes. But Ethan had a mischievous glint in his eye.

"Come on," Ethan coaxed, "It’ll be the perfect prank for Snapchat!" After much cajoling, and against his better judgement, Timmy finally agreed. Ethan slipped the diaper onto Timmy, both of them laughing at the ridiculousness of the situation.

As soon as the diaper was in place, though, something strange began to happen. Timmy’s laughter faded as he felt a peculiar sensation. It soon turned into discomfort then into outright pain.

He felt his body shrinking, his muscles weakening. He tried to stand, but his legs collapsed beneath him, no longer strong enough to support his weight. His clothes became too big, hanging loosely off his rapidly diminishing frame.

Ethan watched in horrified fascination as Timmy’s body seemed to regress. Timmy’s hands, once calloused from playing baseball, now became soft and tiny. His features gradually changed, his face rounding out, wrinkles smoothing away.

"Ethan!" Timmy cried out, his voice becoming higher in pitch, "What's happening to me?" Ethan was speechless, unable to comprehend the surreal transformation unfolding before him.

The process was slow and Timmy’s look of fear gradually softened, replaced by confusion, then blankness. His eyes, once filled with intelligence and wit, were now wide and innocent.

Meanwhile, the room seemed to grow larger, or was it he who was growing smaller? His clothes were now a heap around him. The only clothing that fit was the diaper.

Ethan watched his best friend's transformation complete. Timmy was no longer there, replaced by a tiny baby, hardly a month old. Timmy’s memories, personality, everything that made him 'Timmy' was erased, replaced by the blank slate of a newborn.

The reality of what happened hit Ethan like a train. He scrambled to remove the diaper, hoping it would reverse the process. But the transformation was permanent. The best friend he grew up with was now his baby brother.

In a panic, Ethan called his parents, unable to fully explain what had happened over the phone. Witnessing the impossible situation themselves, they were equally shocked. But what could they do? Timmy was gone, and in his place was a helpless baby.

In the days that followed, they tried to adjust to the bizarre turn of events. Ethan's parents decided to raise the baby as their own, a decision spurred more by the inability to explain the unexplainable rather than desire.

As for Ethan, he found himself navigating through a whirlpool of guilt, regret and loss. He had unknowingly triggered this transformation, turning his best friend into his baby brother. The playful prank had turned into a tragic tale.

The baby, once Timmy, had no awareness of his past life. He cooed and gurgled happily, needing only the basic attention. He was oblivious to the somber mood that hung heavily in the house.

Ethan’s guilt pushed him to take the role of a big brother. It was the least he could do for Timmy. He fed him, changed him, and held him close, whispering apologies no one but he understood.

Sometimes, in the quiet moments, he would look into the baby's eyes and see a hint of his old friend, But it was wishful thinking. Timmy was gone, replaced by this innocent being.

Despite the initial grief, life had a way of moving on. Ethan and his family slowly adapted to their new reality. Acceptance replaced shock, and eventually, they even found joy in their new family member.

The baby grew, his laughter filling the house once again. He was loved, cared for and cherished. The sorrow of the transformation faded, replaced by the happiness that the baby brought them.

Ethan never forgot his best friend. He remembered their shared laughter, their silly arguments, and he even kept the baby's secret. He held on to the hope that one day, he might find a way to bring Timmy back.

For now, he was content. The baby was loved, and in some strange way, Timmy was still with them. It wasn't the same, and it could never replace the bond they once shared, but it was something. In the end, that was all that mattered.