10 Doctor Who Episodes That Were Almost Completely Different
9. A Good Man Goes To War
The opening chunk of A Good Man Goes To War revolves around the Doctor going on a recruiting spree, gathering up a group of allies to help him storm Demon's Run and rescue the kidnapped Amy Pond, along with her newborn child.
Despite most of these allies being new additions to the Whoniverse, the whole thing works out great (Vastra, Jenny, and Strax were so popular that they became recurring characters for the next few years), but even so, it does feel like there's somebody missing: namely, the one and only Captain Jack Harkness.
If the Doctor is calling on his friends to help him in his time of need, then why doesn't he call on Captain Jack? His absence was noticeable, but there's a real-world explanation for it. Writer Steven Moffat was going to include Jack in the episode, but scheduling conflicts with actor John Barrowman prevented this from happening.
But just imagine how A Good Man Goes To War would've played out if Barrowman had been part of the cast. The broader story would've probably been the same, sure, but Jack's enormous personality would've dominated the entire episode, and it's highly likely that he would've had a lot more screen time than any other supporting character.
After all, as we learned in Bad Wolf... Jack = ratings.