My father and brothers and I often deliberately mangle pronunciations just because … well, we’re sick twists and enjoy doing it. Common mispronunciations:
Chester’s drawers (pun intended)
You-tit-ilty
new-cue-leer
pick-em-up (truck)
fam-damn-bly (usually preceded by the word “whole,” making it something of a spoonerism of "whole damn family)
swell foop (fell swoop)
orvital (orbital) – there’s a long story about a funny exchange between my father an my youngest brother over an orbital sander, Orville Wright and bicycles. It takes a long time to tell.
Except that half the people who live in the area usually pronounce it as “RON-see”. 
A girl I taught preschool with in Florida referred to crayons as ‘crowns’. “The red crown and the blue crown go together and make…purple!”
An ex-boyfriend from Massachusetts called potatoes, “podaddoes”. His whole family did it, bugging me endlessly.
But that’s not what the automated announcements on the streetcars say…
Well that’s just ridiculous. Everyone knows it’s pronounced “pertaters,” or just “taters,” if you’re in a hurry.
Not cay-ro. Karo, like the syrup. If you give it that long a sound they’ll have your head.
Personally, I like Marseilles. You know, mar-sayles.
I’m going to refrain from reading the thread, to keep from going ballistic over people claiming that their or other peoples’ pronunciations are “wrong”.
However, I have to share this little tidbit with you: my dad, who otherwise speaks with a standard Midwestern accent, pronounces “robot” like “ro-butt”. You can’t take all of Kansas City out of the man, I suppose.
That reminds of when I first moved to Athens, Ga and worked at a record store which also sold tickets. A customer called up and asked for “wrasslin” tickets and another employee actually had to get on the line and tell me he meant “wrestling”. (I’m from the south and my momma’s from Alabama but this pronunciation was out of my experience.}
My grandma always told me to watch out for “ant bids”. I always said it too, but I’ve got a sneaking suspicion now that she meant to say ant beds. You normals probably refer to them as ant hills.
Sometimes, my friends from scary midwestern places make fun of me for drinking wooder, as most people in the English speaking world instead drink water.
I recently learned how to pronounce “ennui”. I thought it was latin, so was pronouncing it (in my head only, having never spoken it out loud) as “N-U-I”. Turns out it’s french, so it’s pronounced “On-Wee”. Weird.