John

John is a fourth grader who debuted in the episode "Arthur's Eyes". Any information on him is not known, but he does get along with other kids at school.

John was in the same kindergarten class as Prunella and Brain, which was revealed in the episode Brain's Shocking Secret. He has been seen in various places around the school, but has been seen in other places outside of school.

Sometimes he is substituted for Steve, but is clearly not related to either Steve or Steve's younger sister Maria in any way, but is most likely friends with both of them.

Physical appearance
John is a rabbit with a white complexion. He wears a tan collared shirt with long sleeves, dark cream colored khakis, has on very noticeable red suspenders, and cream colored shoes. He is bald, but does have fur.

John also wears rectangular lensed glasses just like Steve does and has a blue backpack. In the episode, The Blackout, his winter attire consists of a chestnut brown coat and a blue scarf. As a Kindergartner he wore a dark blue sweater, long gray jeans, and dark blue shoes. He also use to have hair as a Kindergartner, but had since had all his hair cut off.

Trivia

 * John likely has a little sister named Lisa.
 * Sometimes this character replaces Unknown Male Rabbit in some episodes like Cents-Less where he was seen in one scene and then the scene changed completely with a new character. He also replaces Steve at times in some episodes as in earlier episodes he was seen talking with Maria.
 * John is in the same fourth grade class as Prunella Deegan, which is coincidence considering he was in the same Kindergarten class with her along with Brain.
 * John's name has appeared on lists a couple more times in some episodes.