Ever read a word that totally makes you forget how it is properly spelled, even though it’s something utterly simple? For example, I never had a problem when some people use their/there/they’re improperly, I always know which is the right one. Or “looser”, I never forget it’s spelled loser, and usually snicker at the kids who types it like that when they try to insult someone.
However, I read a review on a website where someone says a movie is hysterious. It took me a good minute to remember that it’s spelled hysterical. Or hilarious. Whichever one the guy was trying to go for in the review.