This thread is a continuation of the original one found here. I have created this continuation thread because the previous thread became unorganized and filled with hundreds of unnecessary comments and duplicates.
Easter Egg Description

So far Ditto is the only non-legendary pokemon that no one has captured yet. It has also been confirmed recently that there are additional easter eggs similar to the eeveloution easter egg. Please post your thoughts. suggestions, and experiments here so that we can solve this as a community.
Potential Clues:
Ditto in the game Pokemon Snap is disguised as a bulbasaur. The Pester Ball is used against the Bulbsaur to have Ditto return to its original form.
Ditto makes it's first appearance in the episode "Ditto's Mysterious Mansion" as a Pikachu. Ditto is unable to fully transform in the beginning and is noticeable due to its face.
If you have tried any of these experiments and they have failed, please let us know.
I try to read most comments and keep track, but due to overwhelming amount of comments I am not able to read all of them.
INTERESTING DISCOVERIES

There is an easter egg where if you hold down and press the main pokeball menu icon down, you will start to see different colors.
Here is what the menu looks like and the colors of the main menu.
These are the same colors as the pester ball which in the game, Pokemon Snap, are thrown at bulbsaur so that it transforms back into a Ditto. The main menu happens to resemble the same colors.
Master ball is within the code, however it is not unlocked at level 40.
Unlocking the Pester ball does not seem possible as of so far. The Pester ball was not found in the code.
These colors also represent the colors of the pokeballs found in the game. Default pokeball (Red), Great Ball (Blue), Ultra Ball (Yellow), and the Master Ball (Purple).
This following is the pokedex description of Ditto we discovered from this code.
"Description": "Ditto rearranges its cell structure to transform itself into other shapes. However, if it tries to transform itself into something by relying on its memory, this Pokémon manages to get details wrong."
Ditto, Bulbasaur, Charmander, Squirtle, and Pikachu are the ONLY pokemon to have a baseCaptureRate of 0.16 and a BaseFleeRate of 0.1. These also happen to be the only starter pokemon. Disclaimer: We have already attempted to revisit the start pokemon and have conducted lots of tests. It is unlikely to solve the easter egg. Please read the Failures List below for more information.
Pikachu can be a starter pokemon. To get pickachu, you have to walk away from the starters and have the respawn up to 5 times until Pikachu appears. This video shows you how.
Ditto has been said to transform into a rock when sleeping to avoid attack.
Geodude, a rock pokemon, has a back that resembles a face which appears to be asleep.
In previous games, Ditto used the same cry as a Poliwag.
Mew/Ditto Theory: It is believed that Ditto was a failed Mew experiment. They are the only two pokemon with the ability to transform.
At the Pokemon GO San Diego Comic-Con Event, the CEO of Niantic stated that there were still additional easter eggs, and that we should "always spin".
In the trading card game, Ditto has his own card for the following forms Pikachu, Charmander, Geodude, Squirtle, and Mr. Mime all with the generic smiley faces.
Porygon has an interesting description related to copying. Here is the description: Porygon is capable of reverting itself entirely back to program data and entering cyberspace. This Pokémon is copy protected so it cannot be duplicated by copying.
THEORIES TO TEST

While you are using the AR camera on one of the starter pokemon or pokemon associated with Ditto (Bulbasaur, Charmander, Squirtle, Pikachu, Clefairy, Geodude), attempt to take a picture with an image of a Ditto in the picture. The camera might have facial recognition.
Look for clues in the titles and names of Pokemon Medals.
Pull down on all possible pokemon to see if there are any clues behind them. Gif is a courtesy of /u/raphpunk
Ditto may be released into the game at the same time when Mew or MewTwo become released because in the past Ditto's spawned in the Cerulean Cave where MewTwo was also found.
Take a picture of all available pokemon in the wild using the in-game camera.
Sometimes the white arrows will be displayed during a pokemon encounter, even though the pokemon is centered in front of you. Turn around and see if there is something hidden behind you or a Ditto. This is most likely a graphical glitch, but we leave no stone unturned.
Ditto may be a South American exclusive Pokemon. Each continent has a regional pokemon (Tauros, Mr. Mime, Farfetch'd, Kangaskhan) except for South America because it has not been released there. Ditto is the last remaining normal pokemon. Ditto's owner is also named Duplica, which in Spanish means 'duplicate'.
Pickachu makes a unique sound when pressed. Perhaps Ditto is a Pickachu with a different sound byte.
Although Ditto can be found in the code, Niantic might be trolling us and still hasn't completed the game mechanics of Ditto. Unlikely, but this view has been shared by many users.
FAILED THEORIES

Rotating eggs around 132 (Ditto's pokedex ID) did not work. This has been tested. It is also poor game mechanics because everyone would be able to reproduce their own Ditto.
Ditto cannot breed with members of its own group, therefore Ditto cannot be hatched from an Egg.
Spinning your caught pokemon in their profile cards has not led to any new discoveries yet.
Talking or saying a phrase to a pokemon will not work because the application does not use the microphone permission.
Battle a Gym using Bulbasaur, Charmander, Squirtle, Pikachu, Geodude, and Mr. Mime in all 6 slots. This is now confirmed to not have worked.
The Red light that comes when catching breaks the molecules of pokemon. Ditto will lose his actual form. Meaning none of your captured Pokemon can be Ditto right now.
Getting random scrambled letters on your iPhone? That is an iOS Unity text glitch. Please avoiding posting about this.
Unlocking Ditto by trying all possible combinations (24 permutations) using the pester ball easter egg did NOT work.
If your game has battery saver on, hold down the pokeball so the menu pops up. Flip the phone over and then release your finger from the screen. Flip it back over, and the menu will remain up, but all the buttons aside from the x will become clickable without going into their proper screens. This will make it much easier for you to play with combinations.
Naming all pokemon excluding the legendaries as Ditto did not work.
Naming the following pokemon to Ditto/Duplica/Imite and evolving/powering them up does not work: Pikachu, Dratini, Bulbasaur, Meowth, Eevee and Poliwag.
Naming Pikachu using the smiley emjoi and the :) characters does not work. http://imgur.com/L3oYdu2
Using the ingame camera does NOT scan QR codes.
Having gym battles and reviving a "defeated" Pikachu named "Ditto"/"Duplica" does not work.
Getting in range of a pokestop and doing the pester ball color trick and then spinning it does not work. There may however be a series of combinations they must be selected at.
Ditto does not spawn if you constantly walk away from the starter pokemon + pikachu.
Taking a picture of all starter pokemon when you first start the game doesn't work. The camera is disabled and the menu is disabled. Perhaps we must take a picture of these 4 in the wild. (Thank you /u/LeonOfLight)
When catching one of the three starters, you cannot take a photo of them with the camera, since the camera is not unlocked until you catch one of them.
Same thing with the Pikachu; walking away from the starters doesn't not unlock you the camera.
You are not able to use the camera other than during a Pokemon encounter. Definition even says "when encountering a Pokemon in the wild"
Using camera to take a photo when the Pokemon appears on the map; it doesn't work.
Using combinations through the Pokeball/drag to one of the 4 options in the menu; attempted the purple in the middle and spinning around the 3 side colors. Did not work.
Tried using google colors, replacing the green with purple (blue, red, orange, blue, purple, red) and the "G" colors that appear on the home screen when logging in (red yellow purple blue). Did not work.
Evolving pokemon that had a similar height and weight as Ditto did not work. We do know that Ditto does not change its height and weight. (Source is from a code dump. Note that there is a height and weight range we could be looking for, not just a 0.3m height and 4kg weight because of the Standard Deviation. The range would be this: Height: 0.2625 M - 0.3375 M Weight: 3.5 Kg - 4.5 Kg)
PokedexHeightM: 0.3
PokedexWeightKg: 4
HeightStdDev: 0.0375
WeightStdDev: 0.5
Evolving a Pokemon (a Ratatata) with these exact stats failed. It did not maintain the same weight and height after evolution. The Pokemon was named Ditto before evolving.
The theory that it isn't released in the public because the "Transform" attack would be too strong is debunked. It is proven the ditto can be captured and does NOT have the Transform attack.
Snapping a picture of Bulbasaur and attempting the pester ball easter egg does not work.
The video circumventing around the internet of a Weedle being hacked into a Ditto is actually a fake video. The Ditto however does indeed exist within the code. Although it has yet to still be seen.