Sebastian Cobb is a scientist whom Lyle Lanley hired to build the North Haverbrook monorail.
Over Cobb's protests, Lanley used shoddy materials throughout the monorail construction process in North Haverbrook, which left it with extensive faults in the brakes and wiring. Unsurprisingly, the monorail crashed on its maiden run, injuring many people and destroying North Haverbrook's economy.
Marge Simpson met Cobb just before the opening of the Springfield Monorail. Suspicious of Lanley, she drove to North Haverbrook to investigate his claim that he had built a monorail there. On arriving, she found the ruins of the North Haverbrook monorail and residents unwilling to talk about the monorail or even admit to its existence. Cobb, however, was willing to talk and filled Marge in on the history of the North Haverbrook monorail. When he heard that the Springfield monorail was about to open, he said, "You just better have a damn good conductor", and the two of them quickly returned to Springfield to try to stop the monorail's grand opening.
They were too late, however, as the Springfield monorail's maiden run was already underway (Cobb apologized for having stopped for a haircut). The brakes had failed and the monorail was speeding out of control. Cobb was able to avert disaster, however, as he advised monorail conductor Homer Simpson via radio to improvise an anchor to stop the train. Homer used the "M" from the monorail sign and did just that, stopping the monorail without serious injury to the passengers.
When the Springfield Skypark-Line, the Monorail reactivates and crushes him. However, it is unknown if Cobb survived or not. 
- Cobb evidently has a vain streak or a lousy sense of urgency, as he and Marge failed to arrive in time to stop the monorail before Homer activated it, due to Cobb stopping for a haircut when he and Marge went from North Haverbrook to Springfield.
- Cobb's accent implies that he may have been raised in Germany.
||The contents of this article or section are considered to be non-canon and therefore may not have actually happened or existed.
The Simpsons: Tapped Out
- This section is transcluded from The Simpsons: Tapped Out characters/Monorail. To edit it, please edit the transcluded page.
Behind the Laughter
Sebastian Cobb's appearance is very similar to Dr. Strangelove from the film Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb.