I've already published a list of 5 characters that TNT could use to pad out their Titans team, besides the already confirmed characters of Nightwing, Starfire and Raven. This is a list of characters that could be used as recurring characters. This list consists of both heroes and villains, and you can also consider anyone from the previous list who isn't chosen to be cast regulars to also be included in this list. The Titans are have been around for fifty years, and in that time they have built a world and a mythology that belongs solely to them as a whole. These are the characters that help to define that mythology and deserve to be not just one-off villains or guest stars, but regularly recurring characters throughout the run of the series. So let's begin.
I really hope that Titans ends up connecting with Arrow, The Flash and Supergirl in the already established universe. We know that not everything exists in this world, though. Gotham and Constantine are noticably out of it, but those shows are also quite different in concept and execution than the others. Constantine is very much rooted in the occult and magic and Gotham isn't really a superhero series, as Bruce Wayne is pre-pubescent and the star of that show is Detective James Gordon. So it stands to reason that those shows would be kept separate as they have different objectives, however, Titans seems to be in the same vein as Arrow and The Flash and so I would love to see that included. The fact that it is on a different network is mostly irrelevant because it is a Warner Bros Television series and TNT is a Time Warner network. I don't see there really being any logistical issues. The biggest reason these shows need to be connected, however, is because of a common enemy. Deathstroke is the quintessential Titans enemy. He needs to be on this show, and while I could accept a different Deathstroke on Titans than was on Arrow, Manu Bennett knocked that character out of the park and I would love to see his Deathstroke face off against Nightwing and the Titans. That said, either way Deathstroke needs to be to Titans what Malcolm Merlyn is to Arrow. He needs to be a big part of the series.
Another reason for Titans to be a part of what is becoming the main DC Television Universe is because of Superboy. Superboy, while never an original member of the Teen Titans, has become a huge part of the team since the Young Justice comic book and even more so with the animated series and the New 52. Superboy is a Titan, and there are a number of fans who think he deserves to be a part of the regular cast. While I wouldn't mind if he ends up becoming a member of the regular cast, to begin with I would like to see him start out as a recurring character because I also want to see him as a recurring character on Supergirl. He should be introduced on Supergirl and he should be a big part of her mythos, but he also needs to be a decent part of Titans. The easy answer to this dilemma is to have him recurring on both shows. Superboy should be the first truly shared character, making regular appearances on both shows. At least, that's how I see it working best, but the shows need to be connected. If they do not connect Titans, it could really end up being a logistical nightmare. Or they could end up just leaving out two of the characters most important to the Titans. Either way, both the fans and the mythology are best served by connecting Titans to the DCTVU.
Terra is a key player in one of the Teen Titans' most important story arcs, The Judas Contract. Terra began as a partner of Deathstroke, sent to spy on the Titans. She becomes close to the Titans during her time with them as a double agent and is eventually redeemed of her betrayal. I just can't imagine anyone doing a Titans television or film series and not adapting The Judas Contract. The Teen Titans cartoon did a version of it, and the Titans television series needs to put their own spin on this, one of the most beloved Teen Titans stories of all time. Also, Terra is a cool character with cool powers (she controls the Earth through an ability called Geo-kinesis). Terra also hasn't been used yet in live action, so this is a character they can, and should, use, whether Titans connects to the rest of the DCTVU or not.
Word on the net is that Gotham is about to introduce the Red Hood on their show. You should understand, this isn't the same Red Hood. That Red Hood is a petty criminal who will one day become the Joker. This Red Hood is a one-time Robin who was murdered by the Joker then resurrected by Superboy-Prime, restored by Ra's al Ghul's Lazarus Pit and is currently a morally ambiguous superhero. Red Hood has strong ties to two members of the Titans that have been confirmed to be in the television series, Nightwing and Starfire, and as Robin was briefly a member of the Teen Titans himself in the 80s. I don't want to see Red Hood be a villain, necessarily, but he should definitely butt heads with Nightwing, who would find his methods over the top. I would also like to be able to see Nightwing and Red Hood connect on some level, especially when it comes to their former mentor, who has already been confirmed to be mentioned on the series, even if he's never really seen.
Since Starfire is definitely going to be a regular, Blackfire is going to have to show up. Blackfire is Starfire's sister and fellow Princess of Tamaran. Blackfire has schemed to dethrone their father, the King, and take over the kingdom for herself. Blackfire is a standard evil twin type of character (although she and Starfire aren't actually twins), and she is very archetypal, but using this character would add so much more dimension to the Starfire character and help to make her a deeper, and thus better, character.
So there you have it, five characters who should have recurring roles on Titans. Anyone you want to see that didn't make the list? Drop it in the comments.