Stacy is sitting on the couch, watching some silly show about interior design or something. You approach her with smile on your face.
"Hey, sis!" you say. "Wanna help me prank Carmen?"
"Ooh... what do you want me to do?" she asks, intrigued.
"Just drink this!" you say, offering her the bowl of water.
"Uh, okay..." she takes the bowl and eyes it suspiciously. "Are you sure this isn't a prank on me?"
"Just do it! This'll be great!" you enthusiastically declare, giving little thought to what a fool you'll look if this doesn't work.
"Whatever you say..." Stacy says with a shrug. She drinks the remaining water and puts the bowl down on the couch next to her.
Then she becomes very still. You hold your breath in anticipation.
Stacy suddenly looks confused, and slowly tilts her head down to look at herself.
"Gyah! What the hell!?" she abruptly cries. That sure sounds like it worked! Your excitement is all over your face, but Carmen - if that is indeed her - is too busy freaking out to notice.
"I... what... how... I'm Stacy!" she shrieks.
"Uh, yeah! I know who you are, sis!" you say, desperately trying not to laugh.
"I... no, I mean, I..."
Before she can explain herself, Stacy, in Carmen's body, rushes into the room. Carmen gets up and shouts at her, "You! You're me!"
"Say what? No, I'm me. You're you," Stacy says in Carmen's voice, barely suppressing her mirth. She's playing along. You grin maniacally, again unnoticed by Carmen.
"No, you're in my body!" Carmen angrily states.
"Uh, what're you talking about?" Stacy asks, not very convincingly. "Is this some kinda lame prank?"
"Gah! Are you trying to steal my life or something? That's it, isn't it! You got sick of your stupid loser life, so you found a way to take someone else's!" Carmen points accusingly. It's a bit weird to see Stacy's body acting so assertive. The real Stacy, meanwhile, looks a little angry at the insult.
Then your mom strides into the room, looking irritated. "What's all this shouting about?" she asks.
Carmen suddenly looks very nervous, a manner more befitting of Stacy's scrawny body. "Ah... I was, uh..."
"Stacy was talking some nonsense about being me," Stacy sniggers. "Said we switched bodies or something."
"Seriously?" Mom looks at "Stacy", actually Carmen, incredulously. "You started a big fight over a silly joke like that? Well, I never. Don't be so hostile to Carmen, Stacy. She's your sister and she should be welcome here..."
As Mom continues to lecture Carmen, Stacy grabs the bowl and slips out of the room, gesturing for you to follow, which you do.
"Nice acting, Stacy," you say quietly.
"John! Did you do this?"
"Yep! It's that bowl. Apparently if two people drink from it, they swap bodies."
"That's amazing!" she squeals with a little jump that makes Carmen look amusingly immature. She looks down at herself with glee. "I feel so pretty and grown-up. You should try it too!"
You hesitantly reach for the bowl. "Uh, okay, I guess I..."
Stacy yanks the bowl away from you. "Nuh-uh! Now it's my turn to switch you with someone! You didn't tell me, so it's only fair that you get a surprise too!"
She runs off, giggling madly. Well, you probably did have this coming. You retreat to your room and wait to see who you end up as.