Marcie, Peppermint Patty’s best friend, is the "brainiac" of the Peanuts crew. She can always be found at Peppermint Patty's heels, Oddly, she calls Patty "Sir,” out of “admiration and misguided manners.”

She, like Charlie Brown, represents a time in Schulz's childhood. In elementary school Schulz was the smartest in his class, skipping ahead several grades. Like Marcie he was the bright one. Marcie is constantly stressed by her parents who prod her into being an overachiever.

Like Peppermint Patty, she doesn’t call Charlie Brown by his proper moniker, opting instead for “Charles,” and also like Patty, Marcie has a secret crush on Good ‘Ol Charlie Brown.