This strip well illustrate's Schulz's emerging skill as a joke writer. Important to is he Lucy's repetition of the word "basketball," which helps illustrate the diverging things the two characters are saying. They're only on the same page in the first panel; none of them are even listening to the other in the others. Characters talk through each other a lot in Peanuts. I'm not even sure this is the first instance of it. The body language of the characters is also important here; in the last panel, Lucy's jumping rope emphasizes that she's more talking to herself than to Charlie Brown.
Psst! I'll be at DragonCon, like starting today. If this blog ends up knocking off a few days that's why, although I usually schedule several strips in advance in these instances. If by some fluke you happen to be at the con, I'll usually be in the board gaming room in a brown "Game Face" T-Shirt.