Theory of EverythingThe two parallel worlds existed before the comic (They shall be referred to as Earth and Oracle). Both equally real, their inhabitants have their own personalities, minds, and lives. The Oracle people see earth in mirrors. Earth people don't know about Oracle, with the exception of perhaps magicians. This explains Violets comment that she wants to feel the world instead if just seeing it, and Violet and Blaze's obsession with their reflections. Omen was somehow transferred to Earth, probably by the puppet Master, who claimed to be pulling the strings. This would also explain why Omen would initially join Doyle- he recognizes him as the Puppet Master's counterpart. Omen was replaced in his own world by his Earth version. Earth-Omen either ended up in a cell, or just didn't participate much in events. As omen's opposite, he would have low self-esteem and not be manipulative, which is practically a requirement in the Crapsack World of Oracle. Omen then created the comic. Him making a connection to a world that already existed makes more sense than creating the entire world, which would give him godlike powers. (If he created the whole world, Doyle and the rest would be a lot more scared and he would have had no problem defeating the Puppet Master.) The creation of the comic formed a third type of character. (Referred to from here on in as 'Comic'). These people are flat, don't have their own decisions or minds. They exist only to predict future events. this is most clearly seen when the two Sages switch. We see Oracle-Sage wreaking havoc on Earth. The comic shows Earth-Sage trapped and asking for help. But the comic also predicts the scene where Lance and Sage fight ("Don't touch me!"), even though Oracle-Sage is the one doing the action, on earth. So the comic has stand-in Comic-characters that exist solely to show events, regardless of who is in what world. This explains why Omen still has a comic counterpart, even though he comes from Oracle. It's not him or Earth-Omen, it's merely an image of the comic to show the future. All direct intervention is done by the 'real' people, of either Earth or Oracle, from mirrors or from the comic. (Like when Blaze or Violet directly address Lance and Cally in the comic). All merely predictive panels in the comic, exist only for that purpose, regardless of which world the characters are in. From there, the regular plot line of the episodes follows. Making Oracle a separate, existing world, even before the comic was created explains several things. When Omen describes himself as having no feelings, it's not because he's just a comic character, but because in his Crapsack World, survival necessitates being manipulative and detached, only in the more gentle Earth was he able to connect with someone. It also explains why him erasing the comic didn't work- The Oracle world existed without the comic, and could still be accessed through mirrors, so he only succeeded in making Blaze and Violet mad, and anyone (like the Puppet master) could recreate the bridge. So the only way to close off Earth from oracle for good, was to defeat the Puppet master, who was first to break the barrier (by sending Omen through).
It's all Cally's fault that the characters from the comic world turned evil.