Transcript:
Lucy approaches Charlie Brown on the lane as he rides his tricycle. She says, “I’ll tell you what, Charlie Brown…”
She runs along beside him and continues, “I’ve got a baby brother at home…I’ll trade you him for your tricycle!”
He rides off and asks, “Absolutely not! What would good would a baby brother do me?” She replies, “I knew you’d say that, and I don’t blame you at all…”
She concludes, “He’s no good to me, either!”
Trivia:
The first reference to Linus
Original comic:



On one hand, Lucy is being selfish and heartless. On the other hand, she’s reacting like any older sibling would. That baby has replaced her as the center of attention and she feels forgotten.
It’s a completely understandable reaction, but it’s pretty heavy, even for early Peanuts.