In an island in the Rhine River near the town of Bingen stands the "Mouse Tower," a building whose fortunes have been checkered over time. But it's best known, and named for, the events said to have befallen a cruel ruler there in the famine year of 974.
This ruler was Hatto II, the Archbishop of Mainz; Mainz was at the time the area's major city, and so it's no surprise that its Archbishop should rule in that time of mixed spiritual and temporal power. What does surprise is how cruelly Hatto treated the folks given to his care. The legend says he rebuilt the ancient tower and used it to harass and shoot commercial travellers if they gave no bribe money.
Then came a year of poor harvests, when Hatto sold the grain stored in his barns to other areas at an excellent price rather than feed his subjects. When they complained, he seemed to soften, and told them all to go to a certain barn and await food there.
They went, but of course got nothing to eat. Hatto sealed them up and burned them, saying they were only good for eating (and, he implied, wasting) grain like vermin. He went home -- to find his castle overrun with mice.
To the tower he fled, but mice by the thousands followed, swimming across the river, gnawing through the wooden door, racing through the tower and eating Hatto up alive.
Here's a version of the tale. Doesn't your mouse look rather mighty to you all of a sudden?