Susie Derkins is a girl that lives in Calvin's neighborhood. She is his only known neighbor. Susie takes school seriously and doesn't slack off on her homework like Calvin does.
Susie believes it isn't a surprise no one has sold a house on their block for 6 years. She is often pelted by Calvin with various objects, including buckeyes, water baloons, and the occasional bowling ball-sized snowball. Despite this, it's obvious they share a physical attraction.
While Susie often ignores Calvin entirely, she is attracted to Hobbes. She often hugs Hobbes or comments on how he is cute (to Hobbes's delight). Although Hobbes does not return the love physically (as he is only a stuffed tiger to her), Susie often becomes the topic of conversation while talking with Calvin.
She has a stuffed animal of her own, a rabbit named Mr. Bun.
Susie reluctantly sits by Calvin during lunchtime at school, but Calvin always decides to sit next to her anyway. In many situations, Calvin would talk about his lunch, portraying it as something disgusting and unappetizing, such as naming his sandwiches revolting things. (An example would be when he told Susie that he mashed some flies into a paste onto 2 pieces of bread, and called it bug butter.)
The love-hate relationship has expanded over the years. In one Valentine's Day strip, Susie angrily pelted Calvin with a snowball, but in the same strip walked away, thinking, "He likes me!" as Calvin thought the same. Another time, they were mercilessly insulting each other, before Calvin said to the reader, "It's shameless the way we flirt."
However, the two never show any love. Susie is instead the target of several of Calvin's pranks, while Susie just tries to be friends. She can often persuade Calvin to play "house" or play with her.
Over the course of the strip Susies love toward Calvin becomes redirected toward Hobbes as she goes out of her way to make a "play" for the tiger, inviting him to her party and only grudingly allowing Calvin to come "if he wants to."
As the only major human playmate Calvin has, Susie factors into many of Calvin's fantasies. In 1991, after Calvin found that he couldn't "throw snowballs when Earth's gravity has increased," the situation warranted the intervention of Stupendous Man, who flew into the air and hit his archenemy, Annoying Girl, with a snowball the size of Susie's head. Susie's mother called Calvin's mother, however, and mild-mannered Calvin recieved the punishment for Stupendous Man's actions.
Susie appeared in two more Stupendous Man stories, in 1992 and 1993, but only as Susie Derkins, innocent bystander. Apparently, Annoying Girl never recovered from being the only foe Stupendous Man vanquished.