When new neighbors move next door, the Harper Quads are instantly drawn to Syd, the kid in their age. They spy on her and try to befriend her in hopes that she will let them hangout in her treehouse. However, Syd has already been warned to beware of the Harper Quads because of their reputation in the block.
- Lizzy Greene as Dawn Harper
- Casey Simpson as Ricky Harper
- Mace Coronel as Dicky Harper
- Aidan Gallagher as Nicky Harper
- Allison Munn as Anne Harper
- Ashley Liao as Syd