@Nilok: I agree dude. But I dont think he's "blowing off his job" just in Sonic 06, it was kinda a big deal and they needed him but I dont count that game as part of any Sonic game story line. Its only real reason was an intro to Silver, which they ended up screwing up Blaze's character and where she came from.
Blaze > Silver (Sonic Rush games rock)
And in Sonic Heroes, they just needed Knuckles to compleye the team.
Im sure they will return him to the Master Emerald, they have to. He is in the Sonic Adventure games, the Genesis games and Comics. Its just his character, they cant take it away.
But from a Game makers point of view, maybe they changed his part cause the Searching for stuff was kinda getting old. WHICH IT WASNT! I Love the Knuxkles parts in the Adventure Games.
Tails started out as Sonic's side kick, and they are a perfect team. Still are (Sonic Rush).
Knuckles was created and surved as Sonic's TOP Rival.
But Is slowly becoming just another side kick cause of Shadow.
Sonic's True Rival. Knuckles!
This shows it in the best way.
http://youtube.com/watch?v=0FYqOeSx9rA
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HOLY CRAP!!!
The Sonic Joins the Brawl Video matches perfectly with the Sonic SatAm there!
http://youtube.com/watch?v=Jt7dxeql_NM