Narita Boy

You get your animal form after clearing the second area and boss of the game.

For 100% walkthrough or if you get stuck use the video at the bottom of my guide Brain5454 made, all credit goes to him.

The chapter stars off with you talking to a guy riding a deer. He will unlock the door off to the left. Keep heading left last the door he unlocked and up to exit the cave. Your goal is to head left or right as the arrows suggest to get a code. Doesn't matter which side you start with.

NOTE
The code for the teleporter was (could be random, not sure, may not work before you activate the things on both left and right)
Red right facing spaceship (2nd last)
Yellow down facing spaceship (last)
Blue 3 dots (3rd from top)

I started heading right, there will be some fighting and at the end there's a gate, go past the gate, don't enter to hit a switch, then enter the gate. Same when you're heading right, go all the way to the right past the gate to hit a switch. Hitting both switches will open a teleport to get your last red symbol. With all 3 symbols enter the colorful teleport. Head left to open the head story thing, once out keep heading left to talk to a baby to get a key. With this key head all the way to the begging where the deer guy is and enter the red door. You get another key which you can use past the colorful teleporter to the right, there you get an orange key which you can use back at the start on the orange door where the boss fight will start.

The boss fight isn't very hard again. It has 2 stages.
Stage 1:
Slow jumping, you want to either dash under him while he's in the air or use the blue side pillars to lure him to one side of the room, jump over him and run to the other side of the room. Jumping over him is much safer. Every 6-7 jumps he'll jump off the screen and try to land on you, watch out for the top screen indicator as to where he lands. He will do this off screen jump 2x and ideally you want him to land in the middle for his second off screen jump. The second jump will knock him off, hit him 3 times MAX and jump dash to the side pillars to avoid his areal attack. Lasts for about 4sec (quicker if you get hit). After you hit him enough times, second stage begins. Took me 4 KOs with 3 hits on each.

Stage 2:
Just like stage 1 but faster. You really want to use the side pillars to jump over him. He will also do 3 off screen jumps, KO after 3rd one. I was still able to land 3 hits before his areal attack.

Story related, can't be missed.

Using the key you received from 'The Pregnant Program', you return to the 'Creators' Tears' and enter the waterfall (use the screenshot below for the code). You've successfully recovered the key from 'Caves of The Eternal Binomial' and you've returned to the 'Access Hall'. Use the key to unlock the 'Master Code-Shifter's Abode' and he will ask you to put an end to the Stallion General in the portal behind him. You will now face off against 'Glaucoma'. After successfully defeating Glaucoma, speak with Master Code Shifter to receive your Stag form, head outside and speak with Stag Master to transform.

Shoulder Bash achievement follows immediately after receiving your Stag form achievement.



Glaucoma Boss Fight on YouTube:

Transcriber code for 'Creators' Tears' to enter the waterfall.