Love them dearly but they can indeed be brats! As a teen, I had a mare who'd get and hold a big mouthful of water when she knew I was coming with her bridle, the better to spew slobbery water on my leg & foot when I made her open up for the bit. I got wise to it by noticing when she had little drops of water clinging to her whiskers, and stood clear... She was mostly a sweetheart, though. And short, like me!
It would probably be an amusing YouTube video if anyone recorded me trying to climb onto a horse these days! Still enjoy the occasional trail ride, though, on someone else's bomb-proof horse.