Ferrets will investigate all opportunities that arise, for good or otherwise.
Ferrets need to be watched!
Sandy and Skippy wrestle for control of the washing machine.
Allowing ferrets to mix with other animals requires rational thought as to the likely hood of injury either pet. Large animals can injure a ferret and a ferret will kill a rabbit or similar pet.
I know of a case where several ferrets escaped from their cage at a pet shop whilst closed, killing the rabbits and guinea pigs plus wrecking the the shop displays. That was an extreme example; ferrets are intelligent, good natured creatures when cared for correctly and treated with respect.