Sis-Tem Error is the first part of the second episode in the fourth season of Dexter's Laboratory. It first aired on April 25, 2003. In this episode, Dee Dee shuts Dexter's lab down by accident and must keep her brother from knowing.
Dee Dee is messing around in Dexter's Laboratory and she turns off the main power switch which turns off the entire lab. She needs to hide this so Dexter doesn't figure out that it was her. When Dexter comes in, Dee Dee has to make everything work so he doesn't notice. Dexter calls out a robot and Dee Dee dresses up as one and does everything and Dee Dee also pretends to be Computer by doing shadow puppets on the screen. When Dexter starts catching on, she pretends that it was Mandark (is actually Dee Dee in disguise) who did it. Dexter leaves and doesn't notice a thing (specially Dee Dee). Then the power comes back on and Dee Dee shuts it off again.