Perhaps they mistakenly thought they were from South Jersey, where this is what everyone does.
The main ones from my brother were hippomotmus and heppecopper (for helicopter). I apparently had some trouble with the “F” in the word shift for a while, amusing my parents greatly.
We’re working on fixing “fravorite” and “lello” at the moment. It’s really interesting to hear her try and say them right. I corrected her and she right then and there she began workingon correcting it by saying “It’s my fffffffffavorite thing” over and over again making sure she said it properly. Must have working on it for about 10 minutes before she felt she had it down. So cute!
She’s 5 by the way.
Pisketti, as mentioned several times - of course.
The Frogs Neck Bridge that connects Queens and the Bronx.
We used to take out books in the lie-berry.
The younger one used to have a problem with L’s.
Dad, I don’t wanna walk anymore, my yegs are kiwwin me.
I used to drive a Folkswagon Corrado - Which is pretty damn accurate IF we lived in Germany!
My son was quite articulate at a pretty young age, but for a while he had a habit of putting an odd sound in the middle of some words.
Every morning he had his bimebim. They weren’t Flintstones, but he liked them anyway.
He often put raindings in his oatmeal.
Sometimes at Grandma’s house he got to ride in a little red wangdon.
I don’t know where those came from, but they went away all by themselves.
My younger son at three says “Frogodile” for crocodile.
Like Angelicate’s child, my son pronounced ambulance something like ambleeance.
Along with **Cyn ** and FernForest’s children, my daughter had lots of trouble with yellow–usually it was lell-yo.
But the most frustrating (and amusing) one occured with my son who consistenly reversed the pronunciation of soldiers and shoulders. Thus he would play shoulders with his GI Joe and sing “Head, soldiers, knees and toes, knees and toes.” I think he was in first grade before this stopped.
My sister has a grandson named Jeremy. One of the young kids on the other side of his family pronounced it “Germy”. Jeremy is almost three now, and my sister still calls him Germy. 
Just as an aside, my 4-year-olds pediatrician says that if there’s no mental delay fueling these speech problems, they disappear by the time the kid is about 7.
My youngest sister used to call water “goody” - I really think this was a mispronounciation because most folks in my family say “water” as if it was spelled “wooder” - I don’t know if that’s a Baltimore thing or a mid-Atlantic thing or what.
My daughter had an odd way of saying “airplane” - I’m not sure how to describe it - it was as if the “p” was replaced with an audible blank, and the entire word was rather nasal. Very odd indeed. She’s since outgrown it - rather than constantly correcting her, I always spoke as clearly as I could and she eventually got it right.
“Pasketti” for me - I think maybe it’s just getting the “sp” sound right that causes grief. Also, “cimmammon” or “cinnaminom” for cinnamon, and I did the “Frogs Neck Bridge” (Throgs Neck Bridge) thing too.
I had a friend who always said “breffix” (breakfast), but he did it as an adult.
My daughter started talking extrememly young, and has been said here a few times, was very articulate.
But that girl could not say Breakfast (breffis) or Yogurt (Gogurt*) for the longest time. She could say Breck, she could say fist but she could not say breckfist… er, breakfast.
And my son said pasketti.
And to answer the question by Mercury, I might have been a little neurotic in that I refused to talk baby talk to my kids. I mean, I did the sing-song voice and cutesy little nonsense babble but much to my ex-m-i-l’s disdain, I refused to call a bottle “baba” or a diaper “diapy” or anything to that effect. Anal? Maybe, but the two older ones started talking in full sentences before they were 1. The baby I unfortunately had considerably less influence over in that way, and she still struggles (she’s 3)
But she does sound damn cute
[COLOR=Silver]*I was glad when Gogurt came out as an actual product (Yogurt in a tub for those uninitiated) because then I could buy that and she was saying it right ;)[/COLOR]
I find it interesting that my son and I have/had the same two words as issues, and it isn’t like I told him mine and he copied. He will soon be 4 years old and is otherwise very articulate - he doesn’t have any trouble with Rs, Ls, or Ys. He speaks more clearly than the other children in his preschool class that I have talked to. BUT…
animal = aminal. We have talked about it repeatedly. I say “It is aNiMal.” He says, “That’s what I said, Mom. Aminal!” I did the same thing with my parents. I remember having the same conversation and finally getting it right in first grade or so. 
Others have mentioned it, but hospital is the other word - comes out Hopsital.
My son does something else that really amuses me. He can’t help but associate new combiantions of words with words that he knows. He calls pine cones pineapples, he calls the Twilight Zone the Twilight Bark (from 101 Dalmatians), and he calls the Ninentendo Game Cube an Ice Cube. He realizes his error but for the life of him can’t seem to remember the correct word instead of his association.
The talk of Jeremy reminded me - there is a boy in his class named Keanu. My son calls him Canoe.
My daughter, 3 1/4 prefers “Emma Emms” to M&Ms.
She also likes “Hangaburgers”.
My daughter got poison ivy on a campig trip when she was three and called it “poison owie.”
My favorite, though, was that almost every morning when she was about two she’d run in the room, arms waving in the air, yelling, “'Ake up! 'Ake up! Da sun is up!”
She also could not pronounce my best friends name, which is Beth, so she called her “The” until she was four. At one point she said to me, “I want a nose ring, like The.” (She obviously did not get one)
Kids seem to have great difficulty with my name: I consistently get called Wol-eeze by teenies. (Awww, bless!). My little sister said appoo instead of apple and that’s still how I think of them…
I was really shocked when someone told me it’s not banilla but vanilla. (I was 10!)
I love it when small children try to be really serious and then say hopsital. It’s soo sweet =)
My daughter was another very early talker who had trouble pronouncing a lot of words. ‘Sh’ was ‘s’, ch ‘t’,’ ‘d’ was a hard ‘g’ for the longest time (goog goggy!), and until a few months ago the soft g sound came out as a soft d. So her name was always Duliette Dorda instead of Juliette Georgia. She’s 5.
Her best mispronunciation was one time on a quiet badminton court, when she asked if I wanted a ‘suck-a-cock.’ (Shuttlecock of course! :D)
My boy says “sketty” for spaghetti, the numbers 13 and 15 are “three-teen” and “five-teen”, he also says “fwee” for three, and “fink” for think.
My favorite, and I will try to get him to say it as much as I can, is his word for the tiny little birds with long beaks that drink nectar. He calls them “humping birds”.
Words mispronounced by my kid, who will be four years old in May:
computer = poncuter
lemonade = wemamade (formerly wenamade)
downstairs used to = soun-dairs
breakfast = bweksist
Craig = Cwed
frosted flakes = frockwet fwakes
mummy = munny (He can say ‘mommy’ just fine, but has to really concentrate to pronouce ‘mummy’ correctly.)
A few days ago we were playing Batman Beats Up Joker. He held a pillow high over his head and declared, “I’m Batman! Bruce Wayne Batman! I will not be denibe!” Heh heh.