Sea Lion Slip-Up is the second half of the twenty-first episode in the first season of Stanley.
The Griffs are getting ready to go to a concert, but Stanley wants to stay home and play.
- David Landsberg as Dad
- Ariadne Meyers as Mom
- Rene Mujica as Harry
- Shawn Pyfrom as Lionel
- Charles Shaughnessy as Dennis
- Jessica D. Stone as Stanley
- Hynden Walch as Elsie