A/N This isn't my original idea. I got it from another HP fanfic writer.
It was the worst day in his life for Herbert Anderson, a seventh year student at Hogwarts School of Witchcraft and Wizardry. Today was N.E.W.T.s day, and he knew that he would fail in Transfiguration. He had managed to master the basic, but was an absolute failure when it came to self-transfiguration. He always needed help getting out of whatever animal he turned himself into, when he managed to turn himself into an animal anyways. He had usually ended up as a piece of furniture and it always took Professor McGonagall awhile to figure out which chair he was. "I hope I manage an animal today," he thought. At least he would get less marks taken off that way.
He was very comfortable with the written test and thought that he would he would get an A or perhaps an EE in that section, but he knew he would be lucky he he even got as high as a D on the self-transfiguration part. After taking the written test, it was time for the practical ones. Herbert sat, very nervously, as he waited for his turn. When his name was called, he wondered if he would be able to make it to the front of the room. He did, and stood there awaiting his professor's instructions. He had to transform a few inanimate objects into other things and a few animals. But then came the dreaded part, self-transfiguration.
"Whenever you are ready, Mr. Anderson, you may begin," said Professor McGonagall.
Herbert slowly took a deep breath and muttered a spell. The instant he said it, he realized it was wrong. He tried to stop, but it was too late. A moment later, the noise started. He opened his eyes, and realized he was taking up a lot more room than he normally would have, even in a desk state. McGonagall was staring at him and then quickly walked over to the fireplace and floocalled the Headmaster. He arrived momentarily, and looked at Herbert.
"What's wrong?" Herbert started to say, but all that came out was a series of mutterings, "Like an engine," he thought. He could tell that both of the professors were trying very hard not to laugh. "Mr. Anderson, it seems as if something went, well, rather wrong with your self-transfiguration today."
"Albus, have you ever seen anything like this happen before?"
"I'm afraid I haven't, Minerva. If I had, perhaps I could figure out what to do."
"Well, you need to do that anyways. I can't have him sitting in here looking like, well looking like that, that thing!"
"It will have to work for the present, Minerva. Now I need to explain to my student what probably happened. You'll need to fill in blanks."
He turned to where Herbert was and began, "Now, you started out with the written test right?"
Herbert nodded, or thought he did.
Dumbledore didn't seem to notice the loud banging, but continued on. "And then you proceeded to practical."
Herbert nodded again.
"After some pratical transfiguration, you then started self-transfiguration. Am I still correct?"
Herbert nodded vigorusly. Loud banging noises came from where his head should be.
"And something went wrong. I'm correct in supposing that something usually goes wrong."
Herbert nodded yet again, but more slowly this time. He didn't want that banging to happen again, but it did, softer, but still there.
"I'm going to try and get you out of this mess. Now just stay still."
Dumbledore reached into his robes and pulled out his wand. He muttered something and a blueish light came out of it. Nothing happened. He did it again, but still nothing happened.
"Doesn't that spell usually cause the person to come out of the transfigured state?" questioned McGonagall, although she obviously knew the correct answer.
"Yes," answered Dumbledore, "strange, very strange."
Herbert tried to ask what was so strange, but there was that banging again.
"Should we tell him?" asked McGonagall.
"We'll have to. There's nothing I can do, unless there's a special spell for this kind of transfiguration."
The two professors then turned to Herbert and said, "We don't know how this happened, but you're a VW Bug."
A/N anyone have a guess about what happened next? Hint, think of a VW Bug with a personality.