Cody is not Kenny's "personal saver". It is Cody's older brother Rufus whom Kenny hopes will fill that role.
Kenny is somewhat of a misfit at his school, both because he is smart and likes to read, and because he has a "lazy eye". Because of these characteristics, Kenny is often teased by his peers. Cody and Rufus are new boys at school, and Rufus is the same age as Kenny. In Kenny's eyes, Rufus is even more of a misfit than he is. Rufus has a country accent and mannerisms, and his clothes are exceedingly shabby. When Kenny first sees Rufus, he is thrilled, because he thinks that the kids will direct their negative attention towards Rufus now instead of towards him.
Kenny thinks that by becoming the new focus of the other kids' torments, Rufus will take upon himself the abuse that used to be directed at Kenny. In this way, Rufus, not Cody, will become Kenny's "saver" (Chapter 2).
Ironically, Rufus ends up not being Kenny's "saver" either. Although the other kids do indeed give Rufus a hard time because he is different, Kenny and Rufus end up becoming buddies of a sort, and through their interactions, Kenny learns some valuable lessons about friendship.