1. Peter Capaldi
Considered for: Sisko in Star Trek: Deep Space Nine
20 years before he'd achieve sci-fi stardom as the 12th Doctor, Capaldi tried out for the part of DS9's Sisko. Back in 1992, he went up against not just Avery Brooks, but also Art Malik, Keith Allen(!) and Anthony Head, some five years before he would book the role of...
Who the captains could have been