The Sontarans are a race of powerful alien warriors with an unfortunate resemblance to baked potatoes in space armor. They were first introduced in “The Time Warrior” in 1973. They have also appeared in “The Sontaran Experiment” (1975), “The Invasion of Time” (1978), “The Two Doctors” (1985), and “The Sontaran Strategem / The Poison Sky” (2008).

Okay, readers, those of you who are not Doctor Who fans better hang on tight, because this character introduction is going to be one of the weird ones.

The mysterious River Song is (probably) a human archaeology professor from (probably) somewhere around the 51st century, and may or may not be a future love interest for the Doctor. We don’t actually know much about her, because she keeps meeting the Doctor “in the wrong order”. The first time he meets her, in Series 4′s “Silence in the Library”, she apparently already knows him extremely well. All her later appearances in Series 5 take place before Series 4, from her point of view. (Time travel, it’s strange.) The outfit shown above comes from the final episode of Series 5, “The Big Bang”.

The Daleks received a colorful design update in the Series 5 episode “Victory of the Daleks”.

Amy — Amelia Jessica Pond — is the Eleventh Doctor’s first companion, introduced in the first episode of Series 5 (2010). Amy is played by Karen Gillan.

Alpha Centauri, one of Doctor Who’s most notoriously silly-looking aliens, appeared in two Third Doctor stories, “The Curse of Peladon” in 1972 and “The Monster of Peladon” in 1974.

Rory Williams was one of the 11th Doctor’s two companions in Series 5 (2010), and is scheduled to return next year for Series 6. Rory is played by Arthur Darvill.