The Twinkie snack cake originally used banana flavor for its cream filling.
James A. Dewar invented the Twinkie in 1930 while working for the Continental Baking Company. The company had machines used to make strawberry shortcake that sat idle when strawberries were out of season. Dewar adapted the idea into a small sponge cake filled with banana cream, creating the snack later known as the Twinkie.
Banana was not the permanent flavor. During World War II, banana supplies were restricted by wartime rationing, so the filling changed to vanilla. Vanilla proved popular and became the standard flavor for most Twinkies, which is why many people assume it was always the original.
The banana version returned only occasionally for many years. Hostess promoted banana-cream Twinkies during a 2005 tie-in with the film King Kong, and the flavor was restored to the product lineup in 2007. Modern versions have used banana purée, but the historical answer remains banana, not vanilla, strawberry, or lemon.