My best friend in high school had two pet rats, Luke and Obi-Wan. Obi-Wan, true to his name, was a sedate white and grey hooded rat who didn't do much more than run on his exercise wheel and squeak for treats. Luke, on the other hand, was the real Phantom Menace!
Their cage was a two-level wire frame, converted from an old rabbit hutch. The only opening was a square on the front of the hutch, held shut with a hook-and-eye latch. There was a removable drawer on the bottom for changing out their bedding.
My friend noticed she seemed to be losing jewelry from the box on top of her dresser, but figured she was either misplacing it or that one of her sisters had been sneaking the jewelry out while she wasn't around. It was beginning to start some major family drama. She even confronted her sisters about the missing jewelry, only to have them become very defensive and confused!
Sure enough, after three weeks of missing earrings and necklaces, she comes back to her room after getting a drink in the middle of the night and spots Luke squirming into the cage through a narrow gap chewed under the edge of the hutch and the removable drawer, dragging a silver chain along in his mouth!
He had a heap of her jewelry hoarded under a pile of shavings in the corner of the cage. She told me, when she opened the cage and started pulling the jewelry out, he sat in the opposite corner squeaking with indignance the entire time.
She and her father did a thorough repair job on the hutch, sealing over the gnawed portions, and she even added a second level of wire to the bottom of the hutch to prevent any further escape attempts.