The first half of the seventh season of Doctor Who may be over, but it may end up being the gift that kept giving for the show's larger mythology. Despite the promise of each week offering a standalone episode, each episode so far has introduced new ideas and concepts for writers to play with in future. Here's five of our favorites.

Undercover Daleks

Congratulations, "Asylum of the Daleks," for the creation of the Dalek sleeper agents - Humans that have been, essentially, hollowed out and replaced by Dalek technology to become mind-controlled agents of the evil pepper pots. Not only is it an idea that manages to make the Daleks just a little bit creepy again for the first time in far too long, it's also something that allows you to go back and watch any earlier Who episode, pick out a character that you didn't quite trust and think, "Yup, there's a unactivated Dalek sleeper agent." Everyone wins!

Historical Companions

Even though the Doctor was, of course, with Amy and Rory up until last week's "The Angels Take Manhattan," we saw in "Dinosaurs In A Spaceship" that he couldn't help but hook up with people to share his adventures with - A reason that the whole "Never travel alone" message from Amy seemed off last week, by the way; it's not as if the Doctor has ever really been a loner before Amy and Rory, after all - including Queen Nefratiti. While the show has played with historical figures throughout its entire 49 year run, I feel as if this was the first time that we've really seen a real life figure essentially act as a companion in a story… And it opened the door to that happening again, and for a longer period of time. How long before we can get Amelia Earhart as a companion, do you think?

Brian Williams, Dad Adventurer

And speaking of companions, I highly doubt that I'm the only person who would like to see more of Rory's dad - A man who didn't quite understand what was going on the first time that he met the Doctor, but was very much on board with doing his bit to save the world the second time. I really liked Brian; there was something about the fact that he just wanted to help in both appearances that I really appreciated. In a series full of extraordinary people, Brian is wonderfully ordinary - but that intentionally makes him stand out, and his ordinary decency and desire to just be useful is something I couldn't help but adore. Can we get a spin-off series for Brian, please?

UNIT Reborn

Thanks to "The Power of Three," we also have a new UNIT to deal with - Or, rather, a repurposed old UNIT that now believes in science instead of military might, and that's a really interesting idea to have around for future use: A quasi-military arm that's more interested in discovery and the truth than conquering or protecting. Whether or not we'll see more of the new incarnation of UNIT any time soon in the show, I have no idea, but there's so much potential here that I can't believe that this organization will stay unused for too long...

Years of Amy and Rory With The Doctor We've Never Seen

A throwaway line in "The Power of Three," but a true gift for those involved with the various Who spin-off material: If Rory and Amy have aged ten years in the time they've spent with the Doctor, then that means there are literally years of unseen adventures together that can appear in comic books, novels, audio plays and whatever other licensed material people want to produce based on this era of the show. Sure, said stories may not be "canon," but since when has canon really been that important to Doctor Who…?