I can't remember its name for the life of me.
It's an animated TV show set in (I believe) a place called Perum
The characters have these PDA-like (Face-to-face chat, camera, teleporter (Called "Porting")) scanners that they use to scan monsters which then become cards. They then went back to the main area where they battled each other using their scanners. They went into this grey room, with two pedistal-like computer things, and a ball hovering in between them with three rings spinning around it in all directions.
The set their scanners in the pedistal and a interactive hologram that lets them choose their team shows up. Randomly, a person is chosen to go first. The person who wins the coin toss (if you will,) says "I challenge X with my Y". They then become the characters challenged. Again, randomly, a map is chosen, and they fight as said characters.
The main character has black hair, and wears a blue shirt. His favorite monster to play as is a green thing, which looks somewhat like him.
His sidekick is a nerdy guy with glasses, and red hair. Yellow shirt (?) His favorite monster is a tall red, strong, blue-horned monster. The red monster and the green monster are leaders of enemy tribes.
His other sidekick is a overweight guy who (obviously?) loves food.
The female character I can't remember much about. Blue eyes(?)
If I recall correctly, all of the monsters were divided into over-worlders, and under-worlders.
In a later season, they travel back in time and meet younger versions of their favorite monsters, and various other extinct monsters.
Thats all I remember. Anyone?