Moon Warp Theory

Potential Credits Warp on JP

On the Japanese version, entrance mod setter, an address known for years that could be used to access the credits if manipulated, is reachable with Bottle Adventure. Meaning yes, it can be manipulated.

Bottle adventure writes 4 rows of 8 bytes.
1st row is a timestamp: with this, we can write whatever bytes we want just by waiting.
2nd row is how long to set the HSW timer for (6000).
3rd row is the actual HSW timer (starts at 6000).
4th row is unknown, but theorized to be the delta timestamp from when HSW is caught (thanks Faschz).

Entrance mod setter is an unsigned short at address 0x1f3736 on Bizhawk. It is default at 65519, but we can potentially moon warp and/or credits warp by changing this.
1) Credits warp: Set this value to 65526 or 65527 and open the door to Mountain Smithy to get a credits warp. There are other values and places that work, but keep in mind that the value will reset to 65519 on new area load, and we need to catch HSW to write this value. Meaning, even if we could write this value, credits warp would need an extra piece of the puzzle to be solved.
2) Moon warp: This would work right now. Never enter a grotto in Termina Field. Enter HSW grotto, set Entrance Mod Setter to 65525. Grotto alt exit to Termina Field grotto. This will take you to Mayor's scene setup 6, which is the Majora fight!

Masks that reach Entrance Mod Setter:
Bremen Mask (4th row)
Circus Leader's Mask (3rd row)
Bremen Mask (2nd row)

The problem:
The 1st row (timestamp) is sufficient to setting any byte it touches to 65525, which is what we want. However, the address is so far down the list of reachable addresses with BA, that the 1st row can't reach this address. If there were 2 more item slots, (or if the address was 2 slots earlier), this would already be completely solved and we would have Moon warp.
The 2nd row and 3rd row will only ever write Entrance Mod Setter to 6000, which is useless. A way to manipulate how long the HSW timer is would fix this, but it seems unlikely.
The 4th row is very likely how much the timestamp has changed since you caught the HSW and when you close the textbox. However, this only seems to update for real bottles. I believe on English I was able to do something to get the 4th row to change for duped bottles, but I don't recall the method.

End note: get the 4th row to update for duped bottles, and Moon warp is possible. Don't be afraid to try stuff out and break the game!