Although this episodes aired in 2002, it was actually produced in 2001 according to the credits.
In this episode, Mom and Dad get into a fight during a game of Scrabble. Dexter and Dee Dee overhear their conversation, causing them to think that Dad was cheating on Mom from the way they talked.
Another episode when Dexter is not in his laboratory in "A Mom & Dad Cartoon"
Another episode when Dee Dee does not appear in "Smells Like Victory"
This episode was aired on June 28, 2002, the same day Nickelodeon's Hey Arnold! The Movie (2002) was released. However, it was a box office bomb.