Yoshpet Early
Note: This page describes a glitch, trick, or exploit. To see others, click here.
Explanation
Normally, to enter Yoshpet, one must obtain the Sewaprolo from Tuskle in Ezofuji. This causes the cliff-face in front of the loading zone to Yoshpet to disappear as Ammy approaches, similar to the wall in front of Sasa Sanctuary. It is possible to reach this loading zone without the key item, though this isn't currently useful in any major category. Yoshpet is already skipped via Wawku Early in every category besides Top Dog. In Top Dog, it is necessary to go through Wep'keer and Ezofuji normally to access the Snowball Area for a Stray Bead.
This can, of course, be done easily via the KT Glitch, jumping directly over the cliff-face. NG-wise, a variant discovered by legoerofeggos uses the vine near the Guardian Sapling to get out of bounds and subsequently trigger a Catapult Jump from a ledge there. From then on, it's only a matter of tackle-jumping to the other side of the barrier (demonstration here).
Older Method
Though it's much more difficult, Yoshpet can also be accessed early in NG through the use of Origin Warp.
First, one would warp to the Mermaid Spring in Kamui from any other spring, then jump on the first possible frame, and land within the water surrounding the spring. Move Ammy out of the spring itself (where Ammy's breath meter is removed and reset, so she never drowns), and allow her to drown. She will respawn at Kamui's origin, which is located below and behind the tunnel entrance to Kamui from Shinshu. She will then be launched upward onto the mountainous out-of-bounds collision. It is then a matter of carefully traversing the slippery collision all the way around the Western side of Kamui, up until the passage to Wep'keer. It is barely possible to perform a Sliding Ground Tackle across the path and to the Northern OoB mountains. From there, navigate behind the Yoshpet Entrance and do another Sliding Ground Tackle to get in.
There are many points where one can easily fall into the void, and much of the collision is invisible, so practice would be needed to perform this trick consistently. Moreover, the large amount of OoB movement required means that this only saves about 1-2 minutes compared to getting the Sewaprolo and entering Yoshpet normally.
Demonstration: https://youtu.be/o-kAk-mB4MA