Charlie Brown and Lucy have a difficult time getting along. Lucy often bullies Charlie Brown for no reason at all; as a result, Charlie Brown often makes comebacks. However, the two are still friends, and can get along.
Charlie Brown's opinion of Lucy
Charlie Brown has a critical opinion of Lucy, as she is always doing mean things to Linus, or dropping fly balls. He also hates how she always calls him names, such as "blockhead", "wishy-washy" and other things like that. He also hates the football gag she pulls on him every year. She even plays this trick on him during the Homecoming game in It's Your First Kiss, Charlie Brown, which leads to Charlie Brown's teammates unfairly blaming him for costing them the game, even though Lucy was at fault.
In the early days of the strip, although Charlie Brown had a fairly better relationship with her than he did in the later days, he often became annoyed by her "fussbudget" personality, and became ever more annoyed when she took that as a compliment.
However, even though Charlie Brown does not like Lucy's mean and crabby personality, he still cares for her and trusts her. In the early days, Charlie Brown would read stories to Lucy, and act as a parental figure to her. Charlie Brown clearly trusts Lucy, as, despite the fact that she always pulls away the football when pulling her famous prank on him, Charlie Brown still trusts her enough to try again the next year, assuming that she will not pull it away that time. He also trusts her enough to tell her his problems when she is in her psychiatry booth.
Lucy's opinion of Charlie Brown
Lucy often mocks Charlie Brown, and abuses him, calling him different insults, such as "dumb" and "weak", although all those insults are false and wrong. Lucy is often unable to realize she is hurting Charlie Brown even though it is completely obvious (an example is the above strip). Sometimes she also teases him on purpose. Although her abuse of him is normally verbal, she does sometimes use physical abuse, most notably with her infamous football gag. Lucy delivers mean remarks with the greatest of ease, usually showing no emotion whatsoever, then moving on with whatever she was doing. When Charlie Brown fails at something, Lucy is quick to point it out, as illustrated by a series of strips from January and February 1964 (later adapted into the script of A Boy Named Charlie Brown) in which she puts together a slide presentation of all of Charlie Brown's faults, and subsequently demands that he pay her a sum of $143 for her services.
In strips from the early days of Peanuts, however, Lucy is shown to have an innocent crush on Charlie Brown. And even later in the strip's run she gives hints to marriage with Charlie Brown. For instance, in the strip from October 5, 1957, Lucy mentions to Charlie Brown that she may someday be the mother of his children, and in the one from June 8, 1960, she mentions to Charlie Brown that if he were to become the President of the United States, she would make a good First Lady.
Lucy shows genuine concern for Charlie Brown's health in a series of strips from July 1979 in which the boy goes to hospital. In the strip from July 19, 1979, she even cries over the matter in front of Schroeder, who finds that strange considering that Lucy had been treating Charlie Brown badly for many years. In the strip from July 27, 1979, she even promises to let Charlie Brown kick the football and not pull it away from him if he recovers.
In the later years of the strip, however, Lucy has also shown to soften up to Charlie Brown. For example, the two occasionally talk about life at the brick wall.