- Peter Duck was one of the things on which it was not safe to disagree with Titty. (SD12)
Peter Duck is Titty Walker's childhood imaginary friend (SD4). He is based on the Norfolk wherryman Mr Duck with whom Titty, with the Swallows, Amazons and Captain Flint spent a Christmas holiday on board the wherry Polly Ann (TOS1,2, SD4; Mr Duck is not mentioned as present on this wherry in SD4).
- Titty and Roger are on their way to discovering Swallowdale: Dolls meant nothing to Titty. Peter Duck was a great deal more useful than any doll could have been. He could always tidy himself away. He never got lost. He had no sawdust to run out. And she had only to think of him, when there he was ... ready for any adventure .... (SD4)
- Titty says: Peter Duck'll be able to fish .... He always liked it. Do you remember how he was always trailling a hook for sharks over the stern of the schooner (SD4).
- When Titty tells the Swallows and Amazons about the hidden valley, Nancy asks "Honest pirate? .... or is it a Peter Duck story". Titty replies "Peter Duck's in it, of course .... but it's all true" (SD4).
- When Titty says they can get to the other side of the road without being seen Susan says "Oh, look here, Titty .... that's a Peter Duck story" but Roger replies "It isn't a story at all" (as they can paddle under the bridge) (SD11).
- The Swallows name Peter Duck's Cave: To John "Peter Duck was one of those things on which it was not safe to disagree with Titty. Anyhow, even for John, he was very nearly real. He had become very real indeed in the story they had made up in the Christmas holidays." So he agreed with the name. "Besides," said John, "if we call it Peter Duck's cave, then when we want to talk of it when there are natives about, or enemies, we can say, 'Go to Peter Duck's,' or 'Fetch it from Peter Duck's,' or 'I left it at Peter Duck's,' or 'We'll meet at Peter Duck's' (SD12).
- Titty added Peter Duck's name to that of Ben Gunn which was carved into the rock inside the cave by Captain Flint more than thirty years ago. She says Ben Gunn belongs to Captain Flint, and Peter Duck is ours (SD13,15).
- Titty's nightmare about the GA being hunted by hounds is a rare instance of Peter Duck being addressed only by his first name: Just to call "Peter" or "Mr Duck" would be enough. But she opened her mouth and no sound came (SD19).
- When Roger was injured in Swallowdale, Titty said You can have Peter Duck while I'm away .... Peter Duck says so too when she left for help leaving Peter Duck to keep Roger company. Roger had said You stay here and let Peter Duck find the woodcutters (SD29).