In Calvin's neighborhood lives only one child his own age, the next door girl Susie. The first time she appeared in the cartoon it had been on the market for four weeks. Whether it is coincidental that the neighbor became a girl, no one knows...
In school they are in the same class, but their attitude towards this institution is very different. Susie shows a more mature attitude towards school, and the work it demands, than Calvin. Her level of learning also clearly exceeds Calvin's, a fact that he knows how to use to his benefit. Susie however, is fully aware that Calvin tries to use her, and therefore she often supplies him with totally wrong information.
Susie must be characterized by an enormous patience. There is no doubt that Calvin is in fact in love with her, but his ways of showing it can only be understood by one person, Susie... He never dares to admit his true feelings to her or anyone else. He has no idea about how to behave when he is around her, and this normally results in fighting.
At school-lunch the two neighbors often end up sitting next to each other, more or less coincidental... Calvin's insecurity is then reflected by pretty bizarre and, not least, disgusting descriptions of the food he has brought.
Their relationship is best described as a love - hate relationship, where Susie stands for most of the love.
Susie is far from deformed, and one should think that she should have no problems with finding other boyfriends than Calvin. However it looks like she has accepted the challenge it is to please this little creep. One of Calvin's ways of showing his affection is sending her a "hate-card" consisting of a black heart with the inscription: "Drop dead!", along with some totally dead flowers from the flower shop's trash can.
As opposed to Calvin, Susie has no imagination. Her suggestions to what the two of them shall do together is limited to playing house. This is, of course, way to realistic and boring for Calvin, and therefore not interesting. What they have in common is equal to nothing, but still there is an attraction between them. This can only be explained in one way: Susie is the only one that cares about (or degrades herself) to get close to Calvin.
Calvin has a crystal clear understanding of the man's position in proportion to women's, and already shows signs of a little sexism. This attitude is probably something he has inherited from his father... Susie however, shows very little understanding for Calvins strong belief that boys are superior to girls, simply because of their sex.