OK, it's not even September yet, and the scrabbling in the walls has started. Maybe the mice know something we don't know about an early winter.
At least it's not rats. I remember seeing some really big rodents hanging around the dining hall dumpsters in college. I'd hate to have those scrabbling in the walls.
If you want to see some really really big rodents, you need to get away from mice and rats and look at capybaras, which can weigh up to 140 pounds. Imagine the holes this guy could chew in your walls:
For some really really really big rodents, we can look to the fossil record and find Josephoartigasia monesi, which had a 21-inch skull and could have weighed as much as 2,200 pounds:
I don't think these things would scrabble in the walls. It would probably be more like this: