Read these notes for more insight. Only if you want to though, this is kind of long already.
Sonic has two personalities, his original personality seen in Sonic Adventure games and Sonic X and is still seen in Japan and the ‘speedster’ archetype personality seen in American media mostly, things like Sonic Prime and the Sonic Movies. I am not saying one is better that the other, I am just giving you some context for later.
“Based on my original projections, I was able to complete my project, Shadow. I designed its mind to be perfect, pure. I will leave everything to him. If you wish, release and awaken it, to the world. If you wish to fill the world with destruction…”
-Gerald Robotnik
SA2=Sonic Adventure 2, it’s a really good story. If you’ve seen the 3rd movie you have pretty much got the plot of that game.
You would think I would talk about the Werewolf/Werehog thing more in this. This is the last time I am going to mention it. The point of this sided is to show you that the moon is weirdly important in Sonic, not as a preview of what's to come.
“I found you... faker.”
“Faker? I think you're the fake around here. You're comparing yourself to me? Ha. You're not even good enough to be my fake.”
“I'll make you eat those words.”
Sonic and Shadow the hedgehog
Acqua Scanlation's translation and Siggie Draws comic
“Why are you following me?”
Shadow turned around to aim the question at Sonic, who followed after him with a grin on his face as he headed into a small path that tapered off the other side of Mission Street.
“I’d like to ask you why,” he responded, both hands circled around the back his head as he gazed up at the night sky. “When were you one to work behind the scenes in order to keep people safe?”
“…I’m not interested in anything of the sort. You think I care about what happens to others? I just can’t stomach the fools on this planet who act with no regard for others. That includes the Doctor, as well as whoever involves themselves with you, too. Don’t get the wrong idea.”
…Several seconds of silence passed. Sonic smirked at the grim look on Shadow’s face.
“Okay. I hear ya. You take care of yourself now. Though, y'know, I’ll bet plenty of folks will be wanting to thank you, if anything like what happened today came out and all.”
“That’s absurd. Even the thought of that’s…”
Shadow stopped in his tracks and turned around, fed up and just about to tell Sonic to be quiet, when…
“…!?”
Sonic had raised his right hand to point at at glowing full moon that backlit the faraway city lights as he looked at Shadow… Moreover, floating just above the moon was the Space Colony ARK, facing their way.
Shadow couldn’t help but gasp at the Ark. At the way that it seemed so detached from the rest of the scenery—at how it seemed divine, even, with the way the moonlight shone on it from below.
The Ark had carried both hope and error with it. It was where Shadow was born, where he had spent much of his time with what was precious to him, and where he had lost a loved one. He had sacrificed so much to protect this planet, the remains of which were now suspended in a vacuum…
Once a year, there was one night that the Ark would appear just above the moon as a natural satellite, as its orbit would so happen to do.
One of Mission Street’s perks was how it offered a good place to view it from. That, plus how the warm city lights shone on the sea—how the light show the night sky would offer looking out on that frigid, unfeeling second moon, as it were—meant that it was one of Sonic’s favourite places to be.
Shadow silently gazed upon the Ark.
No one understood what he could be thinking at that moment—how much of the truth and how many memories of those past events were still left etched in his heart. But the very fact he was silent seemed to provide an answer to Sonic’s question.
Taking it as such, Sonic slowly lowered his hand. Shadow watched as he did, finding the motion telling…
…Before Sonic pointed at his own face with that same hand, showing nothing but a wide grin.
“You waste my time…!” Shadow spat.
He went towards a motorbike parked behind a thicket on the road—a large one for military use which he had seemed to prepare in advance—and mounted it.
Sonic looked like he was about to say something, when Shadow revved the engine to deny him the chance to…
“…There’s no need for two.”
A full moon overlooked the starry skies above Mission Street, a trendy avenue lined with businesses and shops.
With that, he bolted off at full throttle. Sonic made no move to chase after him. Though he always sported a grin on his face, there was some part of it that showed a tinge of regret as he watched Shadow go.
Black Doom confirms in Sonic x Shadow Generations that Gerald in the one the picked Shadow’s ‘form’ in other words look. This could also explain why the Biolizard is a lizard and Shadow is a ‘Hedgehog’, it’s because when Gerald got to pick what the ultimate life from looked like he picked a Hedgehog and when he was making it himself he just worked with what he had.
“I'm letting go of that destructive anger. But I will continue to fight. Fight... with your wish in my heart. Your wish for everyone to have a chance to be happy.”
Shadow the Hedgehog
“Hahaha, Sonic! I think I've discovered what the ultimate life form is... it might be you!”
"Every world has its end. I know that's kinda sad, but... That's why we gotta live life to the fullest in the time we have. At least, that's what I figure."
Sonic the Hedgehog
Sonic (the series) is mainly about how technology should leave nature alone. I mean hell the main bad guy is a rogue inventor who takes little animals to use as batteries for his inventions and the good guy is someone who chooses to be homeless to live in nature. It just feels in the spirit of the franchise to have Sonic be the true ultimate life form and not Shadow. Despite the fact that in canon Sonic has never (truly) won a fight against Shadow.
To be clear I don’t think it is out of character for Sonic to go and see something pretty the one night a year you can see it. It is actually remarkably in character. But why the ARK? Why did he go out of his way to find the best spot to see the ARK of all things. HE DID NOT KNOW HE WAS GOING TO SEE SHADOW, this isn’t about showing Shadow.
You can stop here if you want to.
“Do you know why I named you ‘Shadow?’ because without light there’s only darkness, but a shadow will show where to find the light. Do you understand? I don’t want you to be driven by darkness. I want you to be happy. Stand in the light with peace in your heart.”
-Maria Robotnik
“Sayonara, Shadow the Hedgehog” talk Shadow out of something
Some people (inculding me) think that Rouge is talking about Sonic and not Maria in that scene. We think that because Shadow doesn't seem like the type to talk about Maria at all, if he does it would only be the 'bad times'/vaguely and because Rouge literally saw Sonic talk Shadow out of using the ARK and into helping them.
“Did your pain eventually go away?”
“No. But in time, I learned there's something even more powerful than pain. The love we felt for each other. That's what you need to hold onto, Shadow. Maria might be gone, but your love will always remain.”
“The light shines even though the star's gone.”
Shadow and Sonic the Hedgehogs
If you are a big old nerd you will know how long I have been work on this. Maybe I will wear this shirt as park of the human/closest cosplay of Shadow.
Please let me know if you have any question or theories.