If a ferret's head can fit through a space, their body will go through as well.
It depends how small, but yes. They are rodents, and they can get into very small spaces, like rats or mice can.
If the ferrets head will fit into the hole, then the rest of their body can go through the hole
Hamsters can squeeze through small spaces because they suck in their bodies as much as they can and get through lots of stuff if they tried hard enough they could get through mice holes, and vents but if your hamster got through a vent or mouse hole you're never getting it back! :(
Hornets and yellow jackets can compress their bodies to squeeze through holes as small as the width of a pencil.
Octopuses belong to a family of animals that has no bones. These animals don't have any exoskeleton like a bug or a vertebrae like a mammal. Rather, they have very tight skin & muscle to replace bones, so they can slip through cracks too small for an animal with bones.
Very carefully
Yes, it can have porosity, or pore spaces, but may not have permeability, or the ability for a fluid to flow through connected pore spaces.
Mice neither like cold nor hot climates. They prefer a more neutral climate. They often nest and live in buildings, and can squeeze through very small spaces.
Ferrets wrestle, tackle, roll, bite, claw, and get away in small spaces. This allows ferrets to fight and beat animals much bigger then them, and it's why they are known for their ferocity as well as their cousins weasels. They are some of the most successful predators for their size ever known, but they still make great pets!
A space a little smaller than your shoulders
Cats are incredible athletes. Their most famous superpower is their sense of balance. They notably can fall off of objects and land on their feet, but not always. They can easily walk along narrow ledges and squeeze through small spaces with ease.
Yes. They don't have skeletons so they squeeze through any tight spot.