Did nobody spellcheck this?

I've come across small spelling errors in books before and always asked how they happened. I can understand missing a letter or swapping them around, but this was a little extreme. Anyone else find misspellings that are just so inexplicably wrong you have to wonder what caused them? Or how they slipped out?[spoiler]It wouldn't surprise me to learn that one was an error with the printer itself.[/spoiler]