Home1) There are Chaos Emeralds
2) There are rings. There are also rings (it looks like Power Rings from SatAM/Archie) and this is the glowing yellow light often seen "radiating" from Sonic's hand.
3) Sonic goes into his super-powerful spindash mode with the help of a power ring and a mysterious crystal that looks like a chaos (or master) emerald shard.
4) It is based off the games. They call him Eggman, which is what they call him in the Sonic games. In the shows and Archie comics, they call him Doctor Ivo Robotnik, or Robuttnik.
5) With the help of the chaos emeralds, I believe just one, Sonic can transform into SUPER SONIC!!! The first TV show with him in it, and it's out of this world awesome!
6) Many a Sonic Adventure fan will remember how Tails could transform his Biplane into a fighter mode in SA? Well, he can in Sonic X! Finally, we see the Tornado in real action!
7) In Sonic X, Eggman's robots are actually somewhat of a match for Sonic, unlike the dumb, stupid, and generally incompetent Swat-bots of SatAM and Archie. These new ones are big and carry a big stick (not literally), but they don't speak softly.
Cream the Rabbit. I mean, she just recently was CREATED, only a little bit a while ago when Sonic Advance came 2 out. I can't believe she's actually in it. She can't be more than 3 quarters of a year old for goodness sake.
Shadow the Hedghog: Not a big surprise, especially with all the hundreds upon hundreds of Shadow fans that have come since Sonic Adventure 2 and Shadow's debut.
Rouge the Bat: Well, here's one that's kinda strange. I mean, she didn't generate lots and lots of fans like Shadow, but I guess she's a pretty popular character.
Big the Cat: This character also made his debut in Sonic Adventure along with E-102. He and his pall Froggy were...different, another total surprise. I've come to the conclusion that they liked to put Sonic Adventure characters in SX.