For some strange reason, I remember Matt Leblanc’s Heinz commercial. I also remember his role in Married, With Children, but the Heinz ad is the more appropriate one.
I also remember Zac Efron’s CSI: Miami role before High School Musical was a gleam in its producer’s eye.
Anyone else? (First roles that made them stars, like Cameron Diaz in The Mask, are out of the spirit of this, I think, especially if that project, like The Mask, was a big-time production.)