One of the most remarkable facts about [Peanuts] is the way its popularity cuts across every kind of classification. People from very young children to the very old admire it, for all kinds of special reasons. Schroeder, the Beethoven-loving character who is usually seen playing the piano when he isn't playing baseball, appeals to people who had never heard of Beethoven before. The little tyrant Lucy is seen by the small fry as a deliciously contrary girl, and by some adults as the typically abrasive female in American life. Linus, with his security blanket, seems to speak to everyone who would like to have a blanket of his own in troubled times. And Snoopy, the beagle who has Van Goghs hanging in his doghouse and a World War I aviator's helmet on his head, is the kind of fantasy dog everyone would like to own. (p. 72)
In the hierarchy of immortal comic strips—Blondie, Little Orphan Annie, Andy Gump, L'il Abner, Krazy Kat,—Schulz has created something unique, more successful than all the others, but paradoxically more fragile. Perhaps it is because the strip is so personal that it elicits an unprecedented identification and affection from its vast readership. People don't take it literally, like Little Orphan Annie, whose characters are real people to some readers. Neither is its appeal pure fantasy shaped into barbed, slightly acid social satire, like L'il Abner. Nor is it a vehicle for the creator's political philosophy, as Little Orphan Annie was for Harold Gray.
Everyone sees something different, and something of himself, in Charlie Brown and his friends. He's everybody's boy. (p. 91)
John Tebbel, "The Not-So Peanuts World of Charles M. Schulz, Part I: Happiness Is a Comic Strip," in Saturday Review (© 1969 by Saturday Review, Inc.; reprinted with permission), April 12, 1969, pp. 72-3, 90-1.