Was superpowered web cam girl Niki Sanders (Ali Larter) named after the character in "One Life to Live," or was it just a coincidence? This Niki's DID gave her a Hulk-like sensibility -- stressed and on the run from mobsters, she started blacking out and discovering that her amoral and super-strong alter ego Jessica (the name of her identical sister killed by their abusive, alcoholic father when they were children) was taken over during the missing time. What made the Niki/Jessica dichotomoy interesting, at least in the first season of the series before it went off the rails, was that the poverty-stricken single mom (her husband being in jail) Niki was continually, almost resignedly victimized by life, while Jessica, scary and psychotic as she was, took control and fought back and sometimes murdered people, all in the interests of improving their lot. The strength became an expression of that divide -- Jessica was intensely strong, while Niki had no power at all, and one of the best early moments for the character came when, as Niki, she broke the nightstick of a prison guard who wouldn't let her hug her son Micah (Noah Gray-Cabey), proving that both sides of the woman had always been capable of accessing her gift.
"My Own Worst Enemy" (2008)
This short-lived Christan Slater spy series, created by Jason Smilovic, was another Jekyll and Hyde variation -- the main character and his alter ego even shared first names with Robert Louis Stevenson's, though the split between his good and evil side was the creation of an implanted chip rather than a serum. Henry's a suburban family man who works as an efficiency expert, while his alter Edward is a trained secret agent -- until, of course the divide that keeps them separate starts breaking down and Henry starts waking up in the middle of gun battles while Edward tries to play dad. It was a goofy premise that actually allowed Slater to play nicely against himself as the two personalities attempted to work with (and sometimes against) each other in order to avoid being discovered, but the series ended with a cliffhanger after only nine episodes.
"United States of Tara" (2009-2011)
Based on an idea by Steven Spielberg and created and executive produced by Diablo Cody, "United States of Tara" centered around Toni Collette as Tara Gregson, a Kansas wife and mother trying to manage several alternate personalities. The series was probably the most grounded attempt at portraying Dissociative Identity Disorder to show up on the small screen, in that the show had a consultant with DID and no interest in using the disorder as an excuse for a character to suddenly show up in a wig and stab people in the shower (twist!). While DID was still used as much as a metaphor for the compartmentalization all people do in their lives as an actual condition, the series' attempt to show someone (and that someone's family) living with it on a day-to-day basis rather than be focused solely on finding a cure made it unique, and one of the few portrayals in which the idea of an easy "cure" is just a myth.