Lucy and Linus van Pelt are brother and sister. Like many siblings, they fight a lot. Lucy normally bosses Linus around, or yells at him, and Linus normally annoys Lucy with his habits. However, every once in a while, they get along.
Lucy's opinion of Linus
Lucy is frequently annoyed by her younger brother, Linus. When Linus was first introduced, they did not seem to get off on the right foot. The first time Linus was mentioned, Lucy tries to trade him to Charlie Brown, and says he is of no use to her. Later in the strip, Lucy becomes more annoyed at Linus. She always bosses him around, and calls him a blockhead.
In the earlier years of the strip, whenever Linus was playing with something that belonged to Lucy, she would tattle on Linus to their mother, who would usually direct Linus to give them back to Lucy, who would smile smugly after getting her own way. Sometimes, she would rub it in after she got her things back. This would annoy Linus to no end.
Lucy is often very annoyed by Linus, and his habits. In particular, she wants Linus to end his attachment to his security blanket. She has tried everything to get him to stop using it, such as hiding it, bribing him, and has even gone so far as to cut it up (to make shapes for a "flannelgraph" and later to make squares for Linus to clean his glasses with). She once makes a kite out of it and "accidentally" lets go of it. The blanket flies around the country and people write to Linus to let him know they saw it. It is eventually rescued by the Air Force when it flew out over the Pacific Ocean. Another time Lucy buries the blanket, causing a frantic Linus to dig up almost the entire neighborhood before Snoopy finds it.
Aside from Linus's security blanket, Lucy does not like a lot of Linus's habits. For example, she doesn't like how he waits in the pumpkin patch for the Great Pumpkin every year during Halloween.
Another habit of Linus that drives Lucy crazy is his patting Woodstock and his bird friends on the head. This seems to be a form of emotional therapy for both Linus and the birds, but Lucy is vehemently against it, mainly because she fears that she and her family will be ridiculed if word gets out that Linus pats birds on the head. In a Sunday strip in 1999 she is even more mortified to discover that her youngest brother, Rerun, has also picked up this habit.
Lucy is also notorious for destroying any aspect of Linus' creativity. Whether it be his elaborate and detailed sand castles, which she destroys by kicking them or running them over with her tricycle; a house of cards, which she blows over (in one strip in which Lucy does this to Linus, who is still a baby, he picks up the card deck and throws it at her); a pile of blocks, which she kicks over; or his drawings, which she crumples up, tears up, and/or throws in the trash burner, she never passes up a chance of stifling his creativity out of sheer meanness or jealousy.
She also likes to boss Linus around. She forces him to watch the TV stations she wants to watch, and get her ice cream or anything else she demands. She thinks of herself as much more important as Linus. She one time makes Linus salute her every time he sees her. Lucy forces him to do many things to show that she's more important than him. For instance, once when she makes him toast, she makes him say, "Thank you, dear sister, greatest of all sisters, without whom I'd never survive!"
However, every now and then she shows love for Linus. For instance, on one occasion, when Lucy demands to know what she has to feel grateful for, Linus replies, "Well, for one thing, you have a brother who loves you..." Lucy immediately bursts into tears and hugs Linus.
Another time Lucy showed care for Linus is in It's the Great Pumpkin, Charlie Brown. When Linus does not come home from the pumpkin patch by 4AM, Lucy gets out of bed, goes to the pumpkin patch, leads her cold, shivering and half-asleep brother home and to his room, pulls his shoes and socks off, tucks him in bed, and covers him up, all quite wordlessly and even angrily storming out of his room once he is asleep. In fact, earlier in the special after stopping at the first house on the trick-or-treat round with the other kids, she asks for an extra piece of candy for Linus (the book adaptation says she asked for an extra apple, but this is yet to be confirmed).
Linus' opinion of Lucy
Linus does many things for Lucy, but he does not do them out of love for Lucy. He does them out of fear that Lucy will beat him up if he doesn't do it. For instance, on March 3, 1995, Linus tells Lucy that just because she is older doesn't mean she can boss him around. When Lucy says it does, Linus decides to agree with her.
Just like Linus annoys Lucy with his annoying habits, Lucy annoys Linus with her bossiness. She likes stealing all the crayons (except black, white, and gray), changing the channel or turning the TV off while Linus is watching it, and forcing him to shower her with lavish words of praise before she will even consider sharing anything with him ("Thank you, dear sister, greatest of all sisters, without whom I'd never survive!" is what Linus was once forced to say before receiving a piece of toast. Then, he said, "How can I eat when I feel nauseated?") Lucy also forces Linus to bring her snacks or something to drink while she watches TV. Lucy once bragged that she played Linus "like a pianist plays a concert grand." Whenever Linus was using something of Lucy's, she would, especially in the earlier years of the strip, tattle on him to their mother who would almost always tell Linus to give the possessions back to Lucy, who would smile smugly. Sometimes, she would taunt and gloat at Linus afterwards.
However, Linus often defuses Lucy's temper through resistance and clever use of his intellect, either logically talking Lucy out of hitting him or confusing her into submission.