After I posted “Hi, Captain Jack Harkness,” I was listening to a podcast about the shows, and the hosts commented on something I hadn’t noticed before.
At the end of this duo, when they’re all in the TARDIS and the Doctor and Rose have saved Jack from exploding, they starting dancing. Remember, in this story arc, dancing is also a euphemism for sex, and it was a little skeevy.
Right when Jack gets on the ship and the Doctor tells him excitedly that he remembers how to dance, one of the hosts pointed out there was an exchange of looks between Jack and the Doctor, and this was the moment that Jack fell in love with him.
So I went back and watched, and… I think I can see it. Maybe I’m forcing myself, but I think I can.
This actually answers a question I’ve long had, something that will come up in a few more seasons. Stay tuned!