I've seen them. I know what they look like, and often catch them whizzing across the road at weasel warp speed.
But their size always surprises me. Every time. I know they are small. But when you look at a picture of a weasel or think weasel, you think bigger. You don't think "oh, a weasel. That's a little bigger than a hamster that is". Or I don't. I go, ooooh a weasel. Wow, it's tiny, every time, the surprise never abates.
I struggle with weasel physics. That the actual weasel is not the size of the concept of weasel in my head.
Ferrets are evil. I have a scar across my nose from where a ferret attached itself to my face by its teeth at a friend's wake a few years ago <outs self>. I had to prise its jaws apart with my thumbs just to get it off. Evil bastard.
I am learning a lot about woodland animals from this thread.
I have returned with the INSANE NEWS that Foosa are real things.
I'm watching Madagascar and as I'm now starting to doubt the wisdom of basing my entire knowledge of the animal kingdom on books and cartoons (thanks only to this thread}, I thought I'd turn to Google to check for accuracy.
I have been in the presence of weasels. It was in the car par at the western end of Froggatt Edge, and I heard the unmistakable sound of aggressive mustelids. Three of them, chittering with rage and sinuously leaping about. I was extremely conscious of my exposed toes peeping from my Tevas; their teeth were much in evidence. As the OP says, the size is all wrong.