Red Potion Collection Glitch [MM J 1.0]

Reference video: https://www.youtube.com/watch?v=kFS40IEeapE

In Majora's Mask, Kotake will give you a bottle filled with Red Potion the first time you talk to her. However, if you manage to fill all 6 bottle slots beforehand in J 1.0, Kotake will give you an "alpha" version of the Hookshot instead.

The reason for this is a little bizarre. It turns out that item 0x11 is both a Red Potion and the "alpha" Hookshot, depending on context. When giving items to Link, item 0x11 is treated as giving the player a new bottle that happens to be filled with Red Potion, rather than item 0x13 which is intended to fill an existing empty bottle with Red Potion. Everywhere else, item 0x11 is treated as the "alpha" Hookshot.

80115A20 is roughly the start of where the game handles giving out item 0x11. The routine is simple: if any of the 6 bottle slots are empty (item 0xFF), then the first available slot to the left will be replaced with item 0x13, and the game will jump to the end of the routine. Otherwise, the game will award item 0x11 as if it were any other item, placing it in the leftmost bottle slot.

Unfortunately, it doesn't look as if anything can be manipulated further. The normal Red Potion item value (0x13) is hardcoded in, and the slot that item 0x11 is written to is fixed to the start address of the array of bottle slots.

Updating this with a question by Glitchesandstuff:
"why do the other bottle items [like Gold Dust or Chateau, which have secondary item indexes] not do the same?"

The reason for this is that the Red Potion is handled differently from the other items. The new bottle with Gold Dust and the new bottle with Chateau in it branch to a subroutine at 80115AA0. This routine is quite similar to the one used for the Red Potion, but the main difference is that if no empty slot is detected, the game skips giving any item.