Adult rats we just got from another family.
The cat's initial reaction to us dragging small rodents through the house:
Although at about 6 this morning the other cat suddenly realized HEY! THERE'S SOMETHING MOVING IN THERE! You know what? These cats let a mouse chew all the way through the wall of the garage and eat the wiring to the sprinkler system, so surely they can just get over the rodents in the living room.
Fourth grade science for December: All About Rats.