Resume : Snoopy is an innocent and good-natured beagle who is prone to imagining fantasy lives, including being an author, a college student known as "Joe Cool" and a World War One flying Ace. All of the character's fantasies have a similar formula: Snoopy pretends to be something, and fails. His short "novels" are never published, and he is consistently shot down by his imaginary enemy. Schulz said of Snoopy's character in a 1997 interview: "He has to retreat into his fanciful world in order to survive. Otherwise, he leads kind of a dull, miserable life. I don't envy dogs the lives they have to live."

Snoopy cannot talk, so his thoughts are shown in thought balloons. In the animated Peanuts films and television specials, Snoopy's thoughts are not verbalized; his moods are instead conveyed through growls, sobs, laughter, and monosyllabic utterances such as "bleah" or "hey" as well as through pantomime. The only exceptions are in the animated adaptions of the musicals "You're a Good Man, Charlie Brown" and "Snoopy!!! The Musical" in which Snoopy's thoughts are verbalized by Robert Towers and Cameron Clarke respectively.

Snoopy's doghouse defies physics, and is shown to be bigger on the inside than the outside.