The "evil twin" is a very old plot device in many forms of entertainment.
Edgar Allan Poe used the device in the short story William Wilson. The story (almost a perfect pattern to the much later "evil twins" of television) deals with two twin, one moral, one amoral. The evil twin keeps doing his bad deeds and the good twin is good and ethical -and, of course, the evil twin gets the good twin into lots of trouble. In a bizarre Poe twist, the evil twin happens to have the same name as the good twin (William Wilson) and he was born on the same day (January 19th -Poe's birthday).
Evil twins were portrayed in the movies such as 1939's The Man in the Iron Mask (based on the Alexander Dumas novel) and Charlie Chaplin's The Great Dictator (1940) in which Charlie plays a nice Jewish barber, who has history's ultimate "evil twin" Adenoid Hynkel (an obvious satire of Adolph Hitler).
Comic books have probably had more different and varied evil twins than any other entertainment genre, with Superman, Batman, Robin, The Flash, Wonder Woman, and almost every other classic superhero (or superheroine) worth their salt being plagued by their own "evil twin."
OK, in doing research regarding TV's evil twin characters, I really didn't find that much material out there, so, I not only looked over the limited data available, but I racked my own memory of all the many "evil twins" on all the countless TV shows I have seen over the past 40 or so years.
As far as I know, I believe the very first ever "evil twin" in TV series history was seen on The Adventures of Superman, a series I never missed as a kid, starring George Reeves, my first ever hero. In 1953, Reeves played a dual role (he actually played three different roles, if you count Superman and Clark Kent as two) of a criminal named "Boulder," who dressed up as Superman (complete with a bullet-proof vest) and extorts money from local merchants (I mean, who is going to turn down Superman?). Reeves, a brilliant and talented actor, never relished playing the role of Superman, and supposedly this was one of his favorite episodes.
"Evil twins" weren't all that prevalent in the 1950s, but in the '60s they were to skyrocket and achieve their greatest fame. In a 1960 episode of the popular Western Bonanza, called "The Outlaws," the "evil twin that is portrayed in an episode that is a stretch" first comes to light. The odds against anyone having an actual "evil twin" who is not related to them in any way are, of course, pretty steep. But in this episode, two outlaw brothers who look exactly like both Hoss and Little Joe (Dan Blocker and Michael Landon) and use the old "switch identities" routine on the Cartwright brothers.
Bonanza, by the way, is TV's all-time "evil twin" TV show -you'd never guess that, would you? "Alias Joe Cartwright," a 1964 episode, features a second Little Joe "evil twin" so Little Joe Cartwright may be the only character in TV history to have two completely different evil twins in two completely different episodes. As if that wasn't enough, the third Cartwright brother Adam (Pernell Roberts) is pitted against his own evil twin (whose name is Tom Burns) in another Bonanza episode. So, three of the four main characters in Bonanza had evil twins. That's a mind-boggling 75% "evil twin" percentage!
The only show even close to Bonanza in evil twins is Gilligan's Island. Seven castaways stranded on a remote, uncharted desert island, right? Nonetheless, three (count 'em -three!) of the seven castaways will be plagued by evil twins: those being Gilligan (a Russian spy), Mr. Howell (by a guy who just wants to spend all his money), and Ginger (by Eva Grubb, a homely girl who becomes glamorous after Ginger gives her a makeover and goes to Hollywood to take over Ginger's identity).
So, Bob Denver, Jim Backus, and Tina Louise all got to chew up the scenery as an "evil twin" (that's three of seven characters, almost a 50% evil twin ratio, second only to the aforementioned Bonanza). Of course, not only do the three evil twins somehow find Gilligan's Island, but they also each managed to escape and make it back safely to the mainland.
In one of TV's evil twin's strangest coincidences, two TV Westerns both featured "evil twin" episodes with the very same title, "Deadly Image," which were both aired within a year of each other. The Maverick episode was in 1961, and The Rifleman episode was in 1962. Bewitched, a show I never watched, featured Elizabeth Montgomery playing the lead, a witch named Samantha, plus her cousin Serena, who is actually more mischievous than evil, and was a recurring role in the series.
Following the Bewitched pattern, I Dream of Jeannie, another of the classic '60s fantasy series, starred Barbara Eden as Jeannie, who also played Jeannie's evil twin sister(also named Jeannie). Jeannie (referred to as "Jeannie II" in the show's scripts), like Montgomery's Serena, was Barbara Eden in a black wig. The Jeannie II character became hugely popular in I Dream of Jeannie and she was featured in nine different episodes.
Barbara Eden's portrayal of Jeannie II is brilliant and extremely convincing (she reportedly received lots of fan mail asking "Who's the actress playing Jeannie's sister on the show?" Major Nelson (Larry Hagman) also got his own evil twin in a two-part I Dream of Jeannie episode (as another '60s staple bad guy, a Russian spy).
An episode of another '60s fantasy series, My Favorite Martian, features Tim (Bill Bixby) having his own evil twin, who, like every other evil twin, wreaks havoc before being stopped in the final climactic scene. Lost in Space had an evil twin of Commander John Robinson (Guy Williams).
Even The Flintstones, the most popular animated show of the '60s, had twin Fred ad Barney doubles. Created by the Great Gazoo, the twin Fred can only say "Yes, yes, yes," and the twin Barney can only say "No, no, no." Like some supposedly evil twins, they are really evil just mindless robots who get the real Fred and Barney into trouble.
Star Trek had an episode, "Mirror, Mirror," where the entire crew of the Enterprise each has their own evil twin counterpart. Leonard Nimoy plays Mr. Spock's double, complete with a goatee (a later "evil twin guy" staple). Star Trek fans will point out that the evil twins are not really all that evil and a few of them are actually more friendly and docile, and in Spock's case, more intensely logical, than their earthly counterparts.
Micky Dolenz of The Monkees played himself and his own evil twin in the Monkees episode "Alias Micky Dolenz." Micky played that evil twin staple -a gangster. (Hmmm, maybe their evil twins played the Monkees instruments?)
Interestingly, the '60s TV series you might expect to have the most "evil twins" would probably be Batman, being how it was so campy and was based on a comic book. But few evil twins episodes came out of the legendary series. The only know evil twin Batman episodes used Liberace as "Chandell" or "Fingers," a great piano player. Chandell had an evil twin brother named Harry, who was played, of course, by Liberace, too. Although Chandell was a villian, he was actually forced into becoming one by Harry, who blackmailed him. The Liberace/Chandell episodes were actually the highest-ever rated episodes of the Batman series.