We had a friend who was always trying to impress us by describing various meals he’d have at fancy restaurants; always mangling the names of the meals.
One of friends said to him, “You’re a regular Bon Vivant”. (except he deliberately pronounced it BON VIE-VANT. It went right over his head; he thanked the guy for the compliment.
To this day we still use BON VIE-VANT.
My wife calls it “Whats-this-here” sauce and I have picked it up from her.
::Mr. Burns:: Let them have thier Tar Tar sauce ::Mr Burns::
Every morning, I get up first in our apartment, because I have to make breff-tist for my fambly.
And every December I wish people “Merry Crip-muff!”
In South Carolina, we drive pick-em-up trucks and serve horse doovers at parties.
Hadios, Amoebas.
When I’m demonstrating something, I often say “Obsoive!”
I thought that Whatsdishea was actually a pretty accurate pronunciation of Worcestershire (Og forbid the British actually pronounce more than half of the letters in a proper noun) 
.
My whole family sometimes says ponsuter instead of computer.
See. Ya learn sompin’ every day. We’ums call um Horse D’Ovaries
I had a camp counselor from Philadelphia who called it brekfixt. And according to my mom, the plural is breakfases.
Garrison Keillor called them hambarugers (based on, of all things, some paper he found in a typewriter in an office supply store). I do that myself occasionally.
I’m from Pittsburgh. We miss pronounce EVERYTHING.
Mucus Garcias.
I distinctly recall a photograph taken in the 1930s by John Gutmann of an advertising sign for some candy company that took up one entire side of a building. Among various cartoons and novelty flapdoodle was the phrase EAT HORSE DOOVERS.
Because I’m mom to a toddler I say EH OH for Hello. (Thank the Teletubbies for that one).
Only I do it with other adults and they aren’t amused.
Because of Mig I say Chet-ohs instead of Cheetos. I call cheese kwee-soh just to annoy him.
I call the computer a cadooda because I once had a student that called it that and I can’t get it out of my head after ten years.
Aluminum is aluminiminum. Not sure how that started.
“Ronery”, after the Jong-Il.
Refritterator.
Futton (rhymes with button.)
Croy-sant (thanks Tom and Ray!)
Because french fries are occasionally abbreviated as “fr fr” on some menus, in my family we call them fur-furs. My mom couldn’t remember that and get it right. She called them “free-frees”, so we say that sometimes now too.
The Waffle House is (predictably) known as the Awful House chez moi.