I read a lot of British children's lit, so I frequently want to add that nice little "u" to favor and color. I also sometimes got confused about punctuation because of the Brit-American disagreements.
The best example of how much I lived in books is my misunderstanding of the word "Yosemite." My parents probably mentioned the park a couple of times in my childhood, so I understood there was some park out there named "Yo-sim-e-tee." However, there apparently was another park called "Yo-se-mite." Quite honestly, it wasn't until my 20's that I made the connection. I never talked about "Yo-se-mite," since it's not something that comes up in normal conversation, but I still somehow made the connection.
There's a great episode of This American Life (thislife.org) called "A little bit of knowledge." It's played a few times, most recently on 7/13/08. I listen to it in its entirety every time it's on, and I've even saved it in my iTunes to listen to whenever I want. I encourage you to listen to it now because it's totally on point. And there's talk of a magical extinct animal--the unicorn.