- Hey, It's That Guy!: Now, wait a second, isn't that Dustin Brooks in the thirdquel?
- The Other Darrin: Raven-Symoné originally played Zenon's best friend Nebula, then Shadia Simmons played her in the Zequel...then Raven again played her in Z3 (though only for a cameo; Nebula's cousin Cassie filled her role).
- Protozoa also gets replaced in Z3.
- Zenon's mom and dad get replaced in the Zequel and don't even show up in Z3.