Possible Clues:

• Homer's progeny
• San Francisco rail system
• One of the Simpson kids
• An animated Simpson
• Eldest Simpson child
• Oakland subway letters
• Brother of TV's Lisa and Maggie
• First name of the only fictional character in Time's list of the 100 Most Important People of the Century
• Toon brother of 103 Across
• Target of Sideshow Bob’s plots