The Quagmire Triplets suffered the same fate as the Baudelaires: their parents and their brother, Quigley, perished in a fire. Duncan and Isadora went to Prufrock Preparatory School, where they befriended the Baudelaires. They are often mistaken for twins since Quigley was supposedly killed, but that does not change their identity. At the end of and were pulled under, to their rescue. It is unknown if they are alive or not, but in The End it is mentioned that the Quagmires are "in circumstances just as dark [...] as the Baudelaires'." Kit also mentions that the last she heard of them was one of the Quagmires calling out Violet's name. Sunny asks which sibling called it, but Kit didn't know. It is most likely that the sibling who called out Violet's name was Quigley. Quigley is then not seen again after The Slippery Slope, as he's presumed to have drowned in the ocean. However later it says in The Penultimate Peril he is looking for his siblings.
- Quigley's first name may be a reference to Lillian Fox Quigley, author of The Blind Men and the Elephant, a children's book based on a poem of the same name discussed in The Penultimate Peril.
- Duncan and Isadora’s names are a reference to Isadora Duncan, an American modern dancer.