Each one was a very important part of the group. I don't strongly dislike any of them.
1)Marco: He's the one I relate to the most. He's funny, clever, and the one I'd probably be the most like if I was in the group.
2)Tobias: I can kind of relate to the loner aspect of Tobias. I don't have it as hard as he does, though. Even without the being a nothlit part.
3)Ax: Ax is one of the two funniest characters, and I adore humor. The fact that he's an alien is amusing and interesting. I don't really blame him too much for keeping information from the group in the very beginning, or being tempted to take orders from Andalite superiors later in the series. It's a reminder that, even though he's part of the group, he's also an Andalite. That is his burden.
4)Jake: I once took a quiz that said I was somewhat like Jake. He's got a big cross to bear, but he's one of the strongest links in the group. They look to him as a leader, and everyone but Ax has some personal connection to him in one way or the other before the series begins.
5)Rachel: One side is a warrior woman, and one side is a mall rat who just wants a normal life. I think she is one of the more extreme characters, and is somehwat interesting.
6)Cassie: My least favorite, because she lets emotion and morals rule her too much. I don't have a high standard of morals, and would rather focus on getting the job done and surviving. Rather than worry about comparing morphing sentient life to Yeerk infestation, or handing over the escafil device unconditionally to the Yeerks and hoping something positive comes from it.
Final Note: It seems Cassie isn't that popular around here.
