Yugioh had several planned things throughout the anime and real-life TCG but was eventually scrapped or realized. It also contains things that we, the audience, felt needed an explanation. In addition, the game and anime also include several mysteries. I thought it would be fun to make a compilation of them. This is the third part of a series!

Yliaster Member – 5D

A mysterious Yliaster member debuted in episode 28 of Yu-Gi-Oh! 5D. That character continued to make several brief appearances through Season 1. He was responsible for manipulating Roman into taking control of the project. In addition, his other dialogue heavily implies that he's the mastermind of the entire Dark Signer plot. However, he was then suddenly dropped off and never mentioned again. Some people speculated that he may have been Zone.

Planned Sixth Signer – 5D

The concept sketch for Yu-Gi-Oh! 5D revealed a scrapped Signer and Signer Dragon that never made it to the actual show or game. It should be noted that the scrapped Signer kind of resembles Crow a bit. This may have been a prototype design for Crow, or his design was recycled into Crow's character. It should also be noted that Rua wasn't meant to be a Signer in the sketch. Therefore, they probably scrapped this Signer when they decided to turn Rua into a Signer.

Rex's Fate and Aki's Involvement - 5D

If the rewrite never happened, and Crow stayed as the final boss, what would Rex Goodwin's original fate be? Was he supposed to be a protagonist or antagonist? In the sketch, he or Roman (unclear) was labelled as "the boss of Dark Signers." If the title was labelling him, does that mean he was the final antagonist, or simply like Roman, where he's defeated earlier than his underlings despite being the boss? Furthermore, if Crow was going to be the final villain the hero faces, does that also mean Yusei, Jack and Aki would face Crow against his Earthbound Immortal?

Colorless, Chaos King of Dark World - GX

When Jaden ventured into the alternate dimension in Season 3 to rescue Jesse, his friends tagged along. His friends were captured by the Dark World monsters and sacrificed to summon the Dark World Fusion Monster, "Colorless, Chaos King of Dark World." Baron successfully tributed all of Jaden's friends during the duel, except for Syrus. The duel lasted for two episodes where the monster was constantly hyped up as the most powerful Dark World monster ever to exist. However, it never appeared because Baron wasn't able to tribute Syrus. Therefore, we never got to see Dark World's only fusion monster, or know anything about its effect.

Super Fusion God - GX

Yugioh has never tried to be realistic. However, this one is just ridiculous. This hypothetical monster that Yubel tried to Summon against Jaden requires fusing 12 monsters, 1 of each level, to Fusion Summon it. This monster was Yubel's ace, and Yubel was actively aiming to summon that monster in its final duel against Jaden. The monster was so powerful that it would've fused the 12 dimensions together. However, Jaden then activates some random trap to use his soul as a fusion material... Yeah... Okay... It's not a scrapped or abandoned plan, but a little explanation would be nice.

Icarus Attack - Zexal

The heroine of Zexal was quite a slap in the face for female fans as she doesn't duel, especially when compared to the other heroines. However, in Zexal 2, they finally gave us one duel from her, and boy, did it not deliver. Her Deck focuses on the Fairy-Type monster. Her ace monster is a Rank 4 Monster that allows her to draw one card. Having a Deck that focuses on one type is fine, except she has Icarus Attack in her Deck. Icarus Attack is a Trap that requires a Winged-Beast monster to play, not Fairy, implying that Kotori's Deck may have some Winged-Beast monster. This relates to her name as tori in Katori means bird in Japanese. Does it mean that Katori has Winged-Beast monsters in her Deck or is she that bad at deckbuilding? You decide. 

Fortuno's Hidden Number - Zexal

In episode 18, after losing to Yuma, Fortuno revealed that he actually has a third and last number that he never got to play in the duel. However, that third number was never shown as Kite took it away from Fortuno when he lost to Kite in an off-screen battle.

Earth Destruction - Zexal

In a Number's (No.96/or No.61) memory, Astral saw the Earth exploding. In addition, in Season 1, Dark Mist claimed that Astral's purpose on Earth was to destroy Earth. It certainly seems like something we're going to delve into, but it never happened. The foreshadowing never amounted to anything, and his purpose was quickly changed from destroying Earth to destroying the Barian World. The whole "destroying Earth" thing was irrelevant, as neither Astral nor the main villains want to destroy it.

23 Dimensions - Zexal

The main reason why Kazuma was helping Faker and Tron was that he found out there were 23 dimensions. Unlike other Yugioh series (e.g. GX), the writer decided to pick such a high number... In addition, coupled with the fact that Astral's original purpose was to destroy worlds and Yuma was searching for his dad, it seems like the series was going to visit the other dimensions, right? Nope! It was simply a throwaway line that served no purpose whatsoever.

Fuya/Nelson's role - Zexal 2

In Zexal 2's Opening "Duel-ism of Mirror", Fuya/Nelson is seen briefly. Several other characters that appeared in the original Zexal were also shown in the anime. They all had episodes dedicated to them showing their life after the tournament arc from Zexal. However, Nelson never got an episode dedicated to him at all. His first appearance was when he suddenly showed up with Droite, Anna, Gauche, etc, to duel against the Barian emperors and then die in that same episode. Was he supposed to get his own dedicated episodes like the other characters? Rumors were saying that he was initially supposed to join the main cast, but it was scrapped.