You clear your throat and start reading the spell out:
The one who stands beneath my gaze
Shall find himself in younger days
Let his body shrink to behold
A boy of exactly eight years old
Youthica Manipula
"Eight?" Josh asks, sounding angry. He suddenly gasps, and body starts shrinking rapidly. His clothes droop over his smaller form, and his skin turns all soft and smooth. His hair grows out a bit, and his legs don't reach the floor anymore. After a few seconds, Josh is replaced by an eight-year-old version of himself.
"No way," he says, his voice all high. You can't help but laugh. "Dude, it actually worked!"
Josh hops off the bed, and quickly grabs his pants and underwear. He's now only 4 feet tall, so his 6-foot clothes are just massive on him.
"Hang on, there's a spell for your clothes," you say, flipping through the book.
"Hey, I don't want to be like this forever!" Josh says, stamping his foot. "Don't--"
"Chill man, I'm just fixing them for now." You look down at your "big" brother and chuckle. "You do want to stay like this for a little while, right? I mean, isn't it kind of fun?"
Josh hesitates. "Okay, maybe a bit."
You flip through the book and find the right spell.
Let the clothes this person wears
Change to match the age he bears
Clothify Youthica
His pants shrink into a little pair of shorts, and his shirt shrinks down into a mini polo. Even his socks and shoes get smaller, until he looks just like a little schoolboy.
"You've got to see this," you say, pointing him towards your mirror. He walks up to his reflection and gapes at himself.
"This is so trippy," he says. "You have no idea how weird this feels." He looks up at you. "hey, do you want me to cast one on you, too?