6 Ups & 5 Downs From Doctor Who Series 12
4. Captain Jack's Fleeting Cameo
We haven't seen John Barrowman's Captain Jack Harkness in Doctor Who since 2010's The End of Time Part 2. Then, as a pretty great surprise during Fugitive of the Judoon, our favourite WW2-attired Time Agent returned, having scooped our three companions up from Earth, in hope of finding The Doctor. He sent back a warning regarding the 'Lone Cyberman', telling them 'not to give it what it wants.' He doesn't meet The Doctor in the episode, but he laid the groundwork ready for The Haunting of Villa Diodati, and the following two-part finale.
However, that was it. Captain Jack didn't return for the rest of the series. This exposition-drop regarding the Lone Cyberman could have been done by anyone, even an unknown character only present to deliver this information. Sure, it was great to see Captain Jack again, as said, but teasing a potential return of such a fan favourite character and leaving us dry was borderline inexcusable.
I just want John Barrowman back for a whole series, okay?