Question: Who was originally cast for back to the future?
Disambiguated questions and answers: question: Who was originally cast as Marty McFly for Back to the Future?
Who was originally cast as Biff Tannen for Back to the Future?
Who was originally cast as Marty's girlfriend Jennifer for Back to the Future?
answer: Eric Stoltz
J.J. Cohen
Melora Hardin
Natural Questions answer: Eric Stoltz (from the Wikipedia article "Eric Stoltz")