Holding hands, the two kids ran to the top of the stairs. Over the slide there was a sign showing an illustration of two people going down the slide together, an adult and a child.
"Look." Mary pointed at the sign. "There are two people there. We can take this slide together." She sat down at the start of the slide, and then tapped in front of her, "Come!"
Billy did. He sat in front of Mary. She then pushed behind her to give them some starting momentum to start going down the slide. As they started to pick up speed, she gripped Billy's torso tightly.
Billy expected a change to happen, and the sign they'd seemed to be a pretty clear hint. Probably, one of them would become an adult again. So far, he felt no changes for himself. They hit a tight turn. Water splashed around them, and Billy felt Mary hold him tighter. Her embrace felt large. Big arms holding him. Making him feel safe.
Billy and Mary finished the slide, reentering the pool with a splash.
Billy looked towards Mary, and yep, she was an adult again. Though, she wasn't quite back to her normal self. She seemed slightly older, and a bit chubbier with her chest seeming noticeably larger.
"I'm an adult again," Mary exclaimed as she looked herself over.
"And you're the only one that changed. I'm still a kid."
Mary turned to Billy. "Hmm. You're also different." She paused. "I think I know what happened." She giggled.
"How did I change?" Billy asked. He looked over himself again, more closely this time. He was still a kid, about 9ish, but there did seem to be something slightly different about him. Slight differences here and there, like being a bit paler, maybe shorter?
"It's probably difficult for you to tell, since you can't see your face, but you look like me. Not exactly like me, but like family you know. I think you're my son now." Mary laughed.
"What? You're my mom?" Billy reacted. He looked at Mary again and saw faint stretch marks at the sides of her stomach. "You got stretch marks."
"I do?" Mary looked down at herself. "I do. I guess there's a new past where I gave birth to you. That's wild."
"It is. How about another slide to change into something different?"
"Nah. Why don't we stay like this for a while."
"Really?" Billy groaned.
"Yep! As your mother, I make the rules, and I say we stay like this." Mary giggled. "Just kidding. But for real, it'd be fun to try for a bit, like I kind of want to try being a mom. Why don't we have a mother-son vacation together sweetie please?"
"Okay. I guess. If you really want to, we can try it out. This whole resort is about trying wild stuff like this after all."
"Yay," Mary cheered. She grabbed Billy's hand. "Come let's leave the pool."