Aeronautic Primates and Other Delights

I'm pondering doing a "Horror on Who" vid for my monthly vid column at Classic-Horror. I'm using as many Doctors as I can. My problem is that there's way too much Classic Who for me to sift through and figure "Oh my, yeah, that's a horror/scary/particularly macabre episode."

So I turn to you folks. What are the really good "behind the couch" stories/moments?