Does Shuckle really produce Rare Candies?

There's a rumor, which has been around for as long as Pokemon GSC has been around, that in said games, a Shuckle holding a Berry Juice will eventually turn it into a Rare Candy. I've not been able to find any reputable source on this (and no, people on forums saying "trust me it works i tried it" don't count as reputable), so I'm curious whether it's actually true.

I do see that one thing people seem to agree on is that it doesn't work in any games other than GSC. This suggests an easy way to unambiguously verify it: look in the disassembly and find the code responsible. But I'm not sure where to even begin, so if anyone here could find that or just give some guidance as to where to look, or give any other convincing argument (video evidence, perhaps?) one way or the other, that would be appreciated.

Solution 1:

No, but Shuckle can turn a Berry into Berry Juice

A disassembly of Pokémon Crystal is available on GitHub, and nowhere in it is code for having Shuckle turning Berry Juice into a Rare Candy.

However, this rumor probably has its origin in the fact that Shuckle can turn a Berry into Berry Juice after the player has visited Goldenrod City. This section of code includes a function that runs after the player has visited Goldenrod City, then has a 1/16 chance of a Shuckle holding a Berry turning that into Berry Juice.

ConvertBerriesToBerryJuice:
; If we haven't been to Goldenrod City at least once,
; prevent Shuckle from turning held Berry into Berry Juice.
    ld hl, wStatusFlags2
    bit STATUSFLAGS2_REACHED_GOLDENROD_F, [hl]
    ret z
    call Random
    cp 6 percent + 1 ; 1/16 chance
    ret nc
    ld hl, wPartyMons
    ld a, [wPartyCount]
.partyMonLoop
    push af
    push hl
    ld a, [hl]
    cp SHUCKLE
    jr nz, .loopMon
    ld bc, MON_ITEM
    add hl, bc
    ld a, [hl]
    cp BERRY
    jr z, .convertToJuice

.loopMon
    pop hl
    ld bc, PARTYMON_STRUCT_LENGTH
    add hl, bc
    pop af
    dec a
    jr nz, .partyMonLoop
    ret

.convertToJuice
    ld a, BERRY_JUICE
    ld [hl], a
    pop hl
    pop af
    ret

Solution 2:

No, Shuckle could never turn Berry Juice into a Rare Candy. That is just a rumor.

Here's a YouTuber going through the disassembled code to debunk it.