Half There is the 12th episode of Sabrina's Secret Life.
Both Sabrina and Cassandra want to try out for the part of Ophelia in the school play "Hamlet", since Harvey is going to play the lead character. Sabrina's audition turns into a disaster when Cassandra ruins her performance by using an invisibility potion to trick her. Soon they both try to get even with each other; but it turns out wrong when the potion gets out of control and they constantly fade unaware. Salem tells them to go to the "Middle of Nowhere" in the Netherworld to find an antidote. Maritza ends up getting the part of Ophelia, even though she didn't try-out.