When Nicky, Ricky and Dawn discover that Britt has been hanging out with their friends without them, they start to question his motives.
- Lizzy Greene as Dawn Harper
- Casey Simpson as Ricky Harper
- Aidan Gallagher as Nicky Harper
- Allison Munn as Anne Harper
- Brian Stepanek as Tom Harper
- Kyla Drew Simmons as Mae Valentine
- Jonah Hwang as Britt
- Siena Agudong as Natlee
- Theodore Barnes as Miles
- Isabella Revel as Avery
- Lou Ferrigino Jr. as Jeff Masterson
- After mentioning it's her birthday, Avery blows the kazoo the same way she did after reading birthdays in The Buffa-Lowdown.
- Britt throws a party for the quads for letting him to start living with them in Quadcodile Dundee.
- This episode premiered alongside the Season 4 and the show’s finale episode, Lasties with Firsties; on August 4, 2018.
- Quadspiracy is a play on conspiracy.
- This episode featured Jeff Masterson who hadn't appeared on the show since Go Hollywood.
- This episode marked the final episode title to have the word Quad featured in it.
- Britt makes his third and final appearance in this episode.
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