In the GB/C version the kid literally calls Link “brother” (にいちゃん (nii-chan)), which is used as a common form of address in Japanese for young men one may not be familiar with, but holds a different nuance in English. This was revised to “dude” on Switch.
On Switch, the kid by the Trendy Game already talks about how Marin likes to spend time on the beach, whereas in the GB/C version he repeats his “You’re asking me when we started living here?” line. This may be to give more of a window for the player to learn that hint.
In Japanese the kid talking about the dream shrine has his text censored like “XXX is inside” whereas in English it’s just “something good is inside.”
The cabinet in the dilapidated house gets new text in the Switch version to reflect its neglected state.
Warp points now get introductory text to encourage the player to check them out.
The Japanese is literally “Whoa! What’s this…? Mysterious power overflowed (from it). Let’s check it out!”
Random non-language fact – Richard and Kiki will react negatively to BowWow, preventing you from taking him farther into the game.
In J Richard gets a semi-extra sentence saying roughly, “I can’t bring myself to like barbaric animals like that.”
In J Richard literally says his servants were possessed by monsters, while in E he just says they went berserk.
On E/J GB/C Richard comments that he knows Link is looking for the key to Ukuku Prairie and asks to strike a deal.
(The full English line is: “So you want the key to Ukuku Prairie, do you? I may be able to help you… Let’s make…a deal, shall we? I want…”)
But on Switch this text was changed in both languages. In E, Richard only vaguely hints that he knows Link is looking for something. In J, he simply says, “Hey, will you do something for me? I’ll give you something nice in return.”
E Switch text matches original E GB text “Smashing! To tell you the truth…” while the E GBC version is inexplicably blander “I am impressed.” (J text is unchanged.) For the full lines see: https://tcrf.net/The_Legend_of_Zelda:_Link%27s_Awakening/Version_Differences#Text_Changes
Upon talking to him again, the Japanese gives him slightly more comedic timing. He starts off saying some line that sounds like it’s straight from a shounen anime: “For the sake of love, justice, and…” Then delivers the punch line in the next text box, “…my personal happiness.”
In English Kiki speaks in third person, but in Japanese he uses the same pronoun that the boys do (おいら (oira)), just in katakana.
(Fun unrelated fact: this is the pronoun Sans from Undertale uses in Japanese. It caused quite a stir when that was revealed.)
Kiki is named サルキッキ (saru kikki) in Japanese, which basically amounts to “Monkey Oo-Oo” since “ki” is the noise monkeys make in Japanese. This also means that while Kiki does say his name in Japanese as well, it sounds slightly more natural.
In the original E GB version, after giving Kiki bananas, he says “Monkees!” possibly a sneaky reference to an old rock/pop band who went by that name. This was updated to “Monkeys!” in E GBC and beyond.
”Monkey business” is a cute touch in English. In Japanese he just says “The monkey bridge is done!” Though it does rhyme a bit.
On GB, Ulrira only gives one hint about the leaves: do something to the crow/raven. It doesn’t even specify that you need to startle it first.
GBC adds hints about bombing places and fighting enemies. Though the English hint for the latter is somewhat vague, saying to watch out because someone might take the ones you have. The J is more straightforward, just saying “the soldiers might have them.”
On Switch there are more detailed hints about which enemies in particularly hold the leaves, with slight differences between the J and E:
J – the knight farthest inside > E – boss trooper
J – knight who loves holes > E – hidey-holes
The crow hint also mentions startling it.
When you get the last leaf, the Japanese reads slightly differently, roughly: “Well, may as well bring ’em to Richard and ask about that key.” (Even though Richard never mentions a key on J Switch.) On Switch, if you get all the leaves before talking to Richard, you get slightly different text.
The owl statue behind Richard’s house has a nice creative translation. The Japanese simply reads “There’s a secret under your feet.”
Next up is Key Cavern and the Animal Village!