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After released from the status tube by Rouge in Eggman's base, Shadow suffers from amnesia after his fall from space in Sonic Adventure 2 and he has to team up with Rouge and Omega to find Eggman for their respective reasons. Later on, Team Dark discovers not only the fake Eggman but also the destroyed Shadow android, which caused Shadow to believe that he himself must be one too. Then Omega assures Rouge that the real Shadow must exist somewhere. One thing: Isn't the real Shadow with you guys for the whole entire time? Of course, in Shadow the Hedgehog, Eggman revealed to Shadow during the final boss that one of his robots saved him from the fall, and that he was never an android after all. Well, thanks for wasting all of our good time for the black hedgehog's character arc, SEGA.
It also should have been extremely easy to check if Shadow was an android. X-ray anyone?
Team Rose's story begins with Amy, Cream, and Big searching for Sonic, Froggy, and Chocola. Cue to the fight and even if they accuse Sonic of stealing Froggy and Chocola after seeing a picture of him running off with the two in a paper, although it was Metal Sonic in disguise., Amy behaves like a Stalker with a Crush towards him and threatens to fight him if he refuses to marry him, forgetting about the real reason they are fighting Sonic.
There is the cutscene where Team Dark appears in front of Team Sonic. Although Tails and Knuckles were in shock to see Shadow alive, all that Sonic has to say is "Talk about stubborn and full of surprises!". Uh, Sonic? Is that a proper way to treat someone who you thought was dead after a tremendous fall into earth? This cutscene was one of the reasons why Shadow's return was a lackluster.
In the scene before the battle against Metal Overlord, Sonic, Tails, and Knuckles use the Chaos Emeralds to transform into Super Sonic and...Tails and Knuckles in super shields. Keep in mind that Knuckles can turn super with the Chaos Emeralds although Tails would have to turn super with the Super Emeralds.
Shadow the Hedgehog is filled with a lot of wall bangers, being another notoriously controversial Sonic game.
In many stages, whenever you attack one of the allies, whether it be a GUN soldier/robot, one of Eggman's robots, or a Black Alien, you will earn yourself a rebuke from your partner accompanied by them. Have they ever realize that same guys that you attacked were the same ones who tried to kill you in the first place?
The GUN Commander blames Shadow for the deaths of everyone aboard the ARK, including Maria, whom he was close to the same way Shadow was. Let's get this straight. How can you blame someone for the deaths of everyone even when they were in progress of being created? How can you blame a hedgehog for Maria's death when it was a G.U.N. soldier who killed her. Better yet, how could you work for a military organization who killed your best friend in the first place? It seems as if that guy hasn't really take any medication for his head when he was a child.
The heroes, particularly Sonic, never bother to show any concern for Shadow's memories and also doesn't even bother to help him regain them. In the Space Gadget stage, for example, along with reminding him of their battle aboard the ARK, Sonic seems to have forgotten to remind him of the time they both teamed up to stop the Space Colony ARK from falling into earth, but he only tells him about the time they fought aboard the ARK and have a race for the Emerald.
As a bonus meta-example, there are actually characters in the game who have made it their goal to help Shadow discover the truth about himself, including going to the ARK for that purpose. Specifically, the Chaotix. The wall banger here is how easily fans dismiss them despite this, with the only real reason given being their silly nature and Vector's flawed voice acting. No matter how he said it, it was a very good thing for Shadow that he found that computer room.
At the start of TLE, Mephiles shows up and shoots Sonic In the Back, in order to make Elise cry. He is a time traveller. He could've done that at any point since Elise met Sonic and bonded with him. One theory is that he simply prefers manipulating people to try and do it for him, and/or is a coward.
Elise apparently never cried, not even once, from ages 6 to 16. Not even when she learned her father was dead. Also, killing her also releases Iblis. She could've gotten a car bomb or sniper rifle, since he had literally all the time in her life to try and kill her.
Speaking of making people cry, Robotnik's plan was to gain the Flames of Disaster from Elise. Yet at the end, he's disgusted by the fact that Mephiles had to make her cry to do so, which was really the only way. In short, Robotnik invaded a kingdom and nearly caused a princess to commit suicide over a plot that he himself believes is morally unjust. Does evil have standards here or not?!
In Silver's ending, Blaze seals up Iblis inside her and has Silver transport her into another dimension. This explains how she could be both from the future and another dimension. However, this is completely ignored in future appearances, meaning Sega drew up one of the most plausible plot points in the mess of Sonic 2006, then retconned it for no reason whatsoever.
I didn't really find the game that bad, but the only redeeming part of the plot is Shadow's story. Silver's is just bland, but the main thing about Sonic's story that was really annoying was his obsession with Elise. When he finds out why Silver wants to kill him, he doesn't care and starts fretting on how the Princess will soon die. When they get back to the present and Rouge and Shadow are nowhere to be found, he doesn't care and starts reading about Elise in a poorly translated newspaper. When Elise dies on the battleship, he begins throwing a fit of a larger dynamic of his reaction when Shadow "died" in SA 2. I know death isn't a light matter, but he feels worse about the death of a girl he knew for less than a day, than about the death of a guy who just sacrificed his life for millions of people who he had a grudge against. On the flipside, I find it quite implausible that Elise when eight years old doesn't cry when she learns of her fathers death, yet cries at age eighteen over the death of a guy that she knew for less than a day. I can really see why Sega fired the writers.