a/n: Rated PG for a minor word, but its not that bad.
disclaimer: the only thing i made up here was the Body switching spell

"Now I will teach you a new sort of Switching Spell. It enables you to make two people switch places," said Professor McGonagall one day in Transfiguration.
"Miss Granger, could you kindly stand over there (she pointed to one side of the room) and Miss Patil please stand over there (she pointed to the other side)."
Professor McGonagall pulled her wand out of her pocket. "Switchusa Hermione and Parvati!" she said.
Hermione and Parvati swapped sides.
"It is important to add the a after Switchus," she said, "otherwise there will be disastrous side effects."
The bell rang and Harry, Ron and Hermione left the room. The day was finished.
"I want to try that thing out," said Harry.
In the common room, Ron stood on one side of the room and Hermione stood on the other.
"Switchus Hermione and Ron," he said, forgetting to add the a.
Nothing happened.
"Oh well," shrugged Harry.
"I'd better start doing some homework," said Ron, hurrying away.
"Homework?" wondered Hermione. "Ron?! Why waste a good Friday evening doing stupid homework?"
This surprised Harry even more.
"What?!?!?!?!?!?!" he exclaimed.
He shook his head and ran off to where ROn was.
Ron was sitting on his bed reading Grade 5 Transfiguration.
"Uh, Ron?" said Harry. "We didn't have any homework!"
"I'm doing this to get up ahead," sighed Ron.
"Since when do you like doing that?"
Ron glared at Harry. "I'm trying to study!" he snapped.
Harry shrugged. "whatever."

That night, dinner was late.
"Im so hungry," moaned Hermione. "I need to eat!"
"Hey, leave those house-elves alone," said Ron.
"Oh not that stupid house elf thing again," groaned Hermione.
Harry watched the two of them argue. What was going on? They were acting weird.
Finally, dinner arrived.
Hermione started to stuff her face.

In the common room later that night, Harry found Ron reading a book and Hermione laughing with Fred and George.
"We need to talk," he said to them.
"But I really need to read this!" shrieked Ron.
"Later," insisted Harry.
They sat down in front of the fire.
"I want to know," said Harry, "why you two are acting so strangely!
"For example, Ron's suddenly been obsessed with homework and house elves and Hermione was moaning about food and homework being a waste off time.
What's going on?"
Ron and Hermione shrugged. Suddenly, Ron gasped.
"The switching spell!" he said. "I just remembered! Professor McGonagall was saying if you didn't say the spell properly, then it would have disastrous side effects! And I'm sure Harry didn't say it right."
"Really?" asked Hermione. "I dont remember her saying that!"
"Thats because you weren't listening!"
"ENOUGH!!" snapped Harry. "How do we reverse it?"
"You say the same thing as before," said Ron.
"But I forgot what I said!"
"Damn!!!" groaned Hermione.
"Ok, er......" said Harry. "Switcheroo Ron and Hermione!"
Hermione appeared to have Ron's head and Ron had Hermione's head.
"Switcheroo Ron and Hermione," said Harry again and the heads swapped again.
"Switchusi Ron and Hermione."
"AAAAAAAAAAAAAAAAAARGHHHHHHHHHHHHHHHHHH!!!!!!!" screeched Ron and Hermione.
They had swapped sides but had joined together, like Siamese twins.
"Switchusi Ron and Hermione." They seperated.
"Switchus Ron and Hermione," said Harry, and nothing happened.
"Whew!" said Ron. "All that reading was driving me crazy!"
"Oh no!!!!!!" screamed Hermione. "I'd better catch up on homework!"
Harry's friends were back to normal.