Groening, the show adopted the concept of a large supporting cast from the comedy show SCTV. Continuity and the floating timeline Despite the depiction of yearly milestones such as holidays or birthdays passing, the characters never age between episodes (either physically or in stated age), and generally appear just as they did when the series began. The series uses a floating timeline in which episodes generally take place in the year the episode is produced even though the characters do not age. Flashbacks and flashforwards do occasionally depict the characters at other points in their lives, with the timeline of these depictions also generally floating relative to the year the episode is produced. For example, in the 1991 episode "I Married Marge", Bart (who is always 10 years old) appears to be born in 1980 or 1981. But in the 1995 episode "And Maggie Makes Three", Maggie (who always appears to be around 1 year old) appears to be born in 1993 or 1994. In the 1992 episode "Lisa's First Word", Lisa (who is always 8) is shown to have been born in 1984. A canon of the show does exist, although Treehouse of Horror episodes and any fictional story told within the series are typically non-canon. However, continuity is inconsistent and limited in The Simpsons. For example, Krusty the Clown may be able to read in one episode, but not in another – however he is consistently portrayed as being Jewish and that his rabbi father has since died. Lessons learned by the family in one episode may be forgotten in the next. Some examples of limited continuity include Sideshow Bob's appearances where Bart and Lisa flash back to all the crimes he committed in Springfield or when the characters try to remember things that happened in previous episodes. Setting The Simpsons takes place in the fictional American town of Springfield in an unknown and impossible-to-determine U.S. state. The show is intentionally evasive in regard to Springfield's location. Springfield's geography, and that of its surroundings, contains coastlines, deserts, vast farmland, tall mountains, or whatever the story or joke requires. Groening has said that Springfield has much in common with Portland, Oregon, the city where he grew up. The name "Springfield" is a common one in America and appears in at least 29 states. Groening has said that he named it after Springfield, Oregon, and the fictitious Springfield which was