One of my ferrets used to stack empty soda cans to build a stairway to get up on the counter. Then she realized that if she went between the counter and the wall on the side she could push her back against the counter and just walk straight up the wall.
She would also go under the dresser and push the bottom drawer out a little, then go into it and push the next drawer out a little until she had built herself a little stairway to get up on the dresser.
My sister had a ferret that would wander off all the time. I'd always find it in my made up bed. He would be laying on his back, with the covers pulled up halfway up his body asleep, right in the middle.