Ferrets are very sweet by nature. They only get "mean" (like most animals) from being mishandled, neglected or abused. They are also very smart and can learn many things. Mine both roll over for treats.
I had one ferret, Lucy, who would move things (ie, small box) across the room to use to get up on something higher (ie, desk), or fold a large rug in half to create a "tunnel" to run thru! They love small spaces and tunnels .
They have strong personalities like dogs and are very social with people and other animals.