10 Doctor Who Episodes You Didn’t Know Were Connected
8. Army Of Ghosts & End Of Days
Series 2 finale Army of Ghosts saw the long-teased introduction of the Torchwood Institute, with head-honcho Yvonne Hartman showing off her organisation's cool sci-fi tech to the Tenth Doctor.
One piece of tech in particular catches the Doctor's eye: a Jathaa Sunglider, which Yvonne tells him was shot down over the Shetland Islands a decade prior. Torchwood means business, and the Doctor is rightfully concerned.
That mention of a Jathaa Sunglider might just seem like random technobabble invented purely for this moment - and it probably was - but this wasn't the last time they appeared in the Whoniverse.
Early on in the Torchwood episode End of Days, a trio of Sungliders are seen hovering over the Taj Mahal, in the wake of the Cardiff rift opening and unleashing space-time chaos.
Clearly, this was just a case of Torchwood reusing readily-available assets, but it can also be viewed as a neat bit of world-building that connects the two shows.