David Farnsworth
| Tertiary character | |
| David Farnsworth | |
|---|---|
 | |
| Gender | Male |
| Species | Human |
| Planet of origin | Earth |
| First appearance | "All the Presidents' Heads" (6ACV23)  |
| Voiced by | Unknown |
David Farnsworth is the Professor Farnsworth's ancestor from the colonial era, and is branded by George Washington's Head as a traitor who produced counterfeit currency. The crew go back in time by licking Washington's head, and after beating up Farnsworth they inadvertently alter history. He is based on the real life counterfeiter David Farnsworth, who attracted attention from Washington due to his counterfeiting and was eventually hanged.
In the alternate timeline in which the British have conquered America, David Farnsworth kills George Washington, and is created a Duke as reward. To return to his time, the crew lick Farnsworth's head and return to the colonial era, where the crew restores history and the Professor hits David Farnsworth "much, much harder - Perhaps too hard."