Imperio

Harry Potter yawned and tried not to look as though he were falling asleep as he tried (and failed) to pay attention to what Professor Snape was saying.

"And as you can see, when you add the boomslang skin, the solution turns purple..."

"Harry!" Hermione Granger hissed, elbowing him sharply in the ribs. Harry jerked awake, his glasses askew.

"Wha- what?"

"You were asleep," she said in an annoyed tone.

"Oh. Sorry."

"Potter - Granger - I'm sure your little conversation is fascinating, but it is highly inappropriate when you are supposed to be listening. Fifteen points from Gryffindor," Snape sneered. "Now, as you will see, the Levitation Solution is now red - approximately the colour of blood. I will now drink the solution, and the effects should take place within ten seconds. I will hover for exactly thirty seconds, and then drop back down."

The class - even Harry - watched eagerly as Snape ladled some of the solution into a glass phial, raised it to his lips and drank. Harry had never seen anyone levitate before - not of their own free will, anyway. He counted down from ten in his mind...nine...eight....seven...six....five...four...three...two...one...

Nothing happened. Snape stood stock-still for a moment, and then -

His right leg began to twitch, and then his left; a look of pure horror on his face, his feet began to dance -

"What the - no! - I -"

His face took on an extraordinary expression, as though trying to fight something - something that, by the looks of things, was winning.

"At first I was afraid, I was petrified!"

The class (the Gryffindor half at least) burst into fits of laughter as the first line of I Will Survive belted out of the Potions master (who, surprisingly, didn't have a bad voice).

"Kept thinking I could never live without you by my side
But now I've spent so many nights thinking how you did me wrong
And I grew strong, and I learnt how to get along
And so you're back
From outer space
I just walked in to find you here
With that sad look upon your face
I should have changed my stupid lock
I should have made you leave your key
If I had known for just one second
You'd be back to bother me!"

Harry could hardly move, he was laughing so hard. Ron Weasley, who was sitting on Hermione's other side, had fallen off his chair and was rolling on the floor, whilst tears of laughter were pouring down Hermione's face as Snape jumped up onto the nearest desk. Draco Malfoy looked appalled and backed away.

"Go on now go
Walk out the door
Just turn around now
'Cos you're not welcome anymore!
Weren't you the one who tried to break me with goodbyes?
D'you think I'd crumble?
D'you think I'd lay down and die?
Oh no not I!
I will survive!
Oh, as long as I know how to love
I know I'll stay alive
I've got all my life to live
And I've got all my love to give
And I'll survive!
I will survive!"

"Is he - all - right?" Hermione gasped through her giggles. "The potion must've gone wrong..."

"It took all the strength I had
Not to fall apart
Kept trying hard to mend
The pieces of my broken heart
And I spent oh so many nights
Just feeling sorry for myself
I used to cry
Now I hold my head up high
And you see me
Somebody new
I'm not that chained up little person
Still in love with you
And so you felt like dropping in
And just expect me to be free
Now I'm saving all my loving
For someone who's loving me!"

"Someone help me get him to the hospital wing," Malfoy said, half angrily, half in amazement. Nobody moved; they were all too busy laughing. "Quickly!"

Crabbe and Goyle, Malfoy's henchmen, swiftly jumped to attention and seized hold of Snape, who carried on singing (and trying to dance) as they frogmarched him from the room, Malfoy in tow. They could hear him singing as he went off down the corridor.

"Go on now go
Walk out the door
Just turn around now
'Cos you're not welcome anymore..."

"That," Harry said, picking himself up off the floor, "has got to be the best Potions lesson ever." Ron and Hermione nodded in agreement, although Hermione looked slightly anxious.

"I wonder what went wrong with the potion, though?"

"Who cares?" Ron shrugged. "Bloody funny, though."