When Derek starts to have a crush on a girl named Kendra (Casey's new study partner), Casey tricks him into changing his laid-back image into a more mature person because he wiped out Casey's report on the computer. While George, Edwin, and Derek are afraid of the mice living in their house they try to kill them, but Lizzie won't allow it and makes the mice her new pets.
- Michael Seater as Derek Venturi
- Ashley Leggat as Casey McDonald
- Jordan Todosey as Lizzie McDonald
- Daniel Magder as Edwin Venturi
- Ariel Waller as Marti Venturi
- Joy Tanner as Nora McDonald
- John Ralston as George Venturi