Professor McGonagall was creeping along the corridor, prepared to take any student out of bed at this hour by surprise. Her paws padded softly along the hard floor, and her whiskers itched her nose.
She heard a scuttling, and a squeak.
A rat was zipping over the floor, slightly bathed in moonlight.
Sometime Minerva couldn't help herself. The rodent looked so deliciously fat and juicy. And cats do eat rats.
Minerva pounced and took rat out with one fowl bite. She gobbled it quickly and delightfully.
She went back to patrolling the corridors, not paying any further heed to the rat.
The next day a student was missing.
After several months and a lot of searching he didn't turn up.
He was slowly forgotten about, even by his friends.
These thing happen, especially during war.
Time passed slowly and that group of students graduated. Many things happened afterwards. The Order of the Phoenix was created. The Head Boy and Head Girl of that year, eventually married and had a few children (They did have do into hiding after a particular prophecy was told, but their best friend was a strong and loyal secret-keeper. They were fine, and their children were very cute.) A lovely couple were saved from the Cruciatus curse, and reunited with their son, who became an extremely gifted wizard, due the guidance of his parents. A known werewolf, and an unregistered Animagus became very rich and very famous upon finding a cure for lycanthropy. And most importantly a very dark wizard was defeated. Along with all the Horcruxes he had made.
Life was good.
No one ever realised Minerva McGonagall ate one of her students. Not even Minerva herself realised she had eaten a young Animagus instead of a normal rat.
Even though there wasn't much difference.
So what do you think? This idea came to me in the shower. Life would be so much better without rats. As ever HP doesn't belong to me yet. Not until I go back in time and write it before it's published. Mwaahahaha. One day you shall worship me. HAHAHAHAHA. Just a little crazy.