Lou helps Gwen build her confidence when she learns that her parents plan to send her to school at the end of the summer. Ava discovers a hot spring at Camp Kikiwaka and enlists Noah to keep it a secret.
- Miranda May as Lou Hockhauser
- Mallory James Mahoney as Destiny Baker
- Raphael Alejandro as Matteo Silva
- Will Buie Jr. as Finn Sawyer
- Shelby Simmons as Ava King
- Scarlett Estevez as Gwen Flores
- Israel Johnson as Noah Lambert
- Lucas Stadvec as Reggie
- The title is a play on the Hot Tub Time Machine franchise.
- Lou's favorite book, Ready Farmer One, is a play on the Ernest Cline novel, Ready Player One.
- Finn is still trying to be a vegetarian.
- Ava and Noah are now certified Lifeguards.
- Camp Kikiwaka now has a Snake Cabin.
- Finn reveals that he loves kindergarten/first-grade so much, he had to do it twice, meaning that he might be able to drive in the seventh grade.
The image gallery for Hot Spring Friend Machine may be viewed here.