I was on a painfully long bus ride with a few college friends, one of whom was Japanese, and we got bored enough to try to teach Miwako how to correct the l-r issue in her accent. She tried hard, but eventually got annoyed with the experiment. “It’s the same sound!” she said. “There is no difference!”
This occurs with all kinds of languages. Try teaching an Anglophone the difference between aspirated and unaspirated consonants and dental and retroflex consonants in Indian languages. (“You mean there are four Ds and four Ts?”). Try teaching an Indian the English th sounds.
My stepmother, who is Hong Kong Chinese (i.e. native Cantonese speaker, although she also speaks Mandarin) can pronouce “L” and “R”, but has trouble with “V”; when she says it, is sounds like “W” (i.e. wegetable, instead of vegetable).
In Wussia, sounds pwonounce WOO!
It is certainly extremely exaggerated, but I don’t think it’s completely illogical. Like I said, in German and other languages that don’t have a “w” sound, the speaker doesn’t have to distinguish between a “v” and a “w”. One can easily learn that new sound, but it’s natural to occasionally slip, either by using the more familiar “v” sound when a “w” sound is needed or by overcompensating and using the more “english sounding” “w” sound instead of a “v”.
But it is extremely illogical to depict a German as consistently substituting W for V and vice versa. As in: “You are wery velcome to driwe my heawy vagon vestvard to the westry to meet the wicar.”
It’s the same as depicting an East Asian consistently substituting L for R and vice versa, as in “Sil Flancis Dlake, Admilar of the Freet.”
In my experience with a couple of Japanese guys here it did distinctly sound they were using the other constant, and always “r” instead of “l” from the examples I can remember, even though I intellectually know about the intermediate sound that’s used in Japanese.
I remember asking one of my Japanese roommates what he rented from Netflix and it sounded like he said “Anna-Rice DAT”, which I thought was some cool indie thriller that I’ve never heard of. Then when he repeated himself I heard a bit more clearly Analyze That.
Disregard this if you’re a fluent speaker of French, but you can’t imagine yourself lazily fluctuating in between perfectly pronouncing the throaty puffs that the “r” represents in crossaint and just substituting our “r” sound? Or doing the same for Arabic, sometimes skipping the throaty puff in “Ahmed”, sometimes not.
I know we’ve met in another thread regarding this and while I can buy that Korean has both, I don’t buy your first example. When I say /SA-RANG/, it definitely sounds different than a true English R. My tongue hits (or almost hits) the spot right behind my front teeth with /SA-RANG/ and comes nowhere close when I say it with an American accent.
The second one, though, is definitely an L sound.
My girlfriend’s mom (Cantonese speaker) has trouble with “V”, too; funny thing is, my girlfriend’s (English) name is “Vivian”.
Note the qualifiers:
The consistent reversals are not only implausible, they’re likely to be impossible!
The Japanese director in Monty Python’s “Erizabeth R” sketch and the Hugh Laurie character in the “Chains” episode of Black Adder are in no way plausible depictions of real people. It’s not simply exaggerated, it’s an otherworldly sort of stage comedy.
In Sarang, it’s more like a Spanish R, which sounds like a “D” to me. (Like in Mira).
But not exactly. As Monty says, there’s an L, an R and a Y in Korean. The family name “이” doesn’t have an L, R, or Y in it at all. It’s actually pronounced “EE”.
The only people pronouncing Ls, Ys, and Rs in front of that family name are English speakers–not Koreans. Granted, you can’t blame them since Koreans with the last name EE, do write their name using the L, Y or R in the front (family preference?), adding to the confusion. But you’ll never hear them pronounce it like that.
I believe spelling it “Lee” has something to do with the Chinese last name and history or something. Beats me. Monty probably knows why. But all three of those family names are pronounced EE.
If their family name really was Lee or Rhee, it would be spelled 리, not 이. If it was really Yi, it would be spelled… well shit, there is no Yee in Korean, is there? So why would they ever spell it like that to begin with?? Beats me. Monty?
My German friend only ever had this happen with “vodka”–she always pronounced it “wodka,” and she explained that this was, in her experience, a regional German thing. Some people in Germany called it “vodka,” others “wodka.”
Language is a funny thing, is it not? 
Maybe it’s a Germanic language thing. naita mentioned that Norwegian doesn’t have a ‘w’ sound, and it’s the same in Danish, except, interestingly, the west-Jutlandian dialect that pronounces almost any ‘v’ sound as ‘w’.
Similar things in Bengali. Standard Bengali doesn’t have s or z sounds, but East Bengali dialects pronounce sh as s and j as z
Hmmn … when my (British) daughter was young she used a ‘w’ for ‘l’ and ‘r’ ‘y’ (‘yellow lorry’ would be pronounced ‘wewwow wowwy’. The speech therapist said the sounds were closely related and it was a speech immaturity that was not that uncommon. it sorted itself out, although the ‘r’ sound took several years to come through.
Now this work incident from a few years back makes sense- our job hired an Asian fellow and put him in charge of supplies. We couldn’t find him all day, and at then end of the day I go to get my coat out of the cloakroom, and he jumps out and yells Supplies! 
I got an illustration of this in a class I TAed. It was a physics of sound and music class for non-physics majors. The professor brought in a machine for recording voiceprints, and we had discussed in class how one’s native language affects the ability to discriminate between sounds in other languages. I had a TA in another class who was a native speaker of Russian, and got him to come to the physics of music class. The professor had him say some sounds that sounded the same to me, but the voiceprints were quite different- evidently, Russian distinguishes between the sounds and English doesn’t.
No, I’ve heard this sort of mistake in real life, though it isn’t very common. The speaker may be confused about a group of consonants in the new language, and get things mixed up with spelling in their native language. It’s rare, but I have heard native Spanish speakers mispronouncing “yes” as “jes”. If the sound doesn’t exist in your own language, it’s entirely possible that you will mistakenly use it in places where it doesn’t belong.
When I was taking Mandarin classes, the ‘L’ sound was common, and indistinguishable from the English ‘L’ to my ears. Keep in mind that this was specific to Beijing-dialect Mandarin. Your local dialect may vary
It was the multiple ‘ts’ pronunciation variants (q, ts, s, z) that gave me trouble, and are very dialect-variable from what I understand. Once while practicing with one of my Chinese friends, she all of a sudden pointed at me and started laughing “Ha ha ha ha! You sound Taiwanese!” I’m not sure why, but there you go…