Not Above a Book...
So tonight's episode of How I Met Your Mother revealed that Ted Mosby has lived his entire life* pronouncing the world "chameleon" not "kuh-meel-yun" but "tchah-mil-ee-on". [*Until 2011, anyway. The show is technically one big flashback, with detours, from 2030.]
I bet that many of us have had similar experiences — even the best-educated. Being an early and voracious reader, in fact, probably makes one more likely to get an erroneous phonetic pronunciation stuck in one's head, oblivious to how it's actually pronounced aloud.
My own memorable equivalent of "chameleon" is the word that I pronounced in my head as "eh-pih-tohm" and realized a bit on the late side was the selfsame word as "uh-pih-tuh-mee".
Some more examples:
A beloved 6th-grade teacher of mine once slipped and said "werewolf" like "weary-wolf". (The class laughed; she blushed, apologized, and admitted that she used to do that all the time as a kid; she became all the more beloved.)
I heard a quite winsome actor refer to a "biopic" on The Late Show with David Letterman as a "by-ah-pik". While I can see thinking that the word would be stressed like "bionic" and thus rhyme with "myopic" if you read it out of context, given that it's a fairly well-known showbiz neologism that combines "bio" (as in "biography") and "pic" (as in "picture") the gaffe was hard to believe.
When I was a kid reading The Invaders, a 1970s Marvel comic book about a group of superheroes that assembled during the 1940s, the characters often referred to the Nazis derogatorily as "Ratzis" — but early on, at least, I didn't get that the word was slang, because I read "Nazi" as "nazz-ee". DC set Wonder Woman back during World War II for a spell around the same time, so that it would sync with the first season of the Linda Carter television series, and it was thanks to that television series that I realized "Nazi" rhymed with "Yahtzee".
The reverse phenomenon can also occur to those of us who grow up in regions with particular accents, even if the denizens don't think of themselves as having accents – which is to say, pretty much everybody. For instance, I recall spelling the word "drawers" as "droors" based on how it sounded.
Anyone want to share their own pet mispronunciations in the comments?