Ethan Allan was an American patriot who fought in the American Revolution. He led the Green Mountain Boys militia.
There was also a baseball player named Ethan Allan, a pitcher who played in the 1920s and 1930s. This may be one of the reasons Robert confused them (along with the phrasing of the question on the history test).
Abner Doubleday is traditionally credited with inventing baseball, though there is some dispute about how much he deserves that claim.