Jennifer Garner, Alias
Roles: Sydney Bristow and Anna Espinosa

Using a special DNA cloning project, super spy Sydney Bristow’s enemy, K-Directorate agent Anna Espinosa, was changed to look exactly like Sydney, giving Garner a chance to play both parts of the “Spy vs. Spy" game.

Jeffrey Tambor, Arrested Development
Roles: George Bluth and Oscar Bluth

Tambor got to play total opposite twins on the FOX drama as the unethical patriarch of the Bluth family and his pot-smoking loser twin brother. Highlights included George shaving Oscar’s head to make the police think his twin brother was actually him.

The Cylons, Battlestar Galactica
Roles: Multiple copies of the seven Cylons played by Dean Stockwell, Callum Keith Rennie, Lucy Lawless, Rick Worthy, Matthew Bennett, Tricia Helfer and Grace Park

Each Cylon had multiple copies, providing plenty of confusion. Particularly interesting were the different Sixes (Helfer) as well as two prominent Eights, Boomer and Athena.

Sarah Michelle Gellar, Buffy the Vampire Slayer
Roles: Buffy Summers and the Buffybot

In one of the creepiest and most hilarious dual roles, Gellar played the titular vampire slayer as well as a robot that looked just like her designed for Spike’s pleasure.

Jensen Ackles, Dark Angel
Roles: Ben and Alec

Genetically-engineered twins, Ben appeared in season 1 as a serial killer and Ackles was so good that they brought him back in season 2 as his less psychotic cloned twin.

Garret Dillahunt, Deadwood
Roles: Jack McCall and Francis Wolcott

In this gritty Western Dillahunt played McCall, the man who murdered Wild Bill Hickok, in season 1. After getting cleaned up, Dillahunt was brought back in season 2 as a new character, the psychotic Francis Wolcott.

Lisa Kudrow, Friends
Roles: Phoebe Buffay and Ursula Buffay

Kudrow played the ditzy Phoebe for many seasons and, in several episodes, she also played her equally hare-brained but more adventurous twin sister Ursula (who originally appeared on Mad About You).

The Cast, Fringe
Roles: Real and alternate universe versions of the characters played by Anna Torv, John Noble, Lance Reddick, Jasika Nicole and Kirk Acevedo

There are two universes which gives Fringe the chance to have two of everyone. Most interesting are the two for Walter and Olivia who are so important they have their own nicknames (Walternate and BOlivia, for Bad Olivia).

Sherilyn Fenn, Gilmore Girls
Roles: Sasha and Anna Nardini

Fenn originally played Jess Mariano’s dad’s significant other in a third season episode intended to be a pilot for a new series. It didn’t happen, so instead Fenn showed up later as the mother of Luke’s daughter.

Ali Larter, Heroes
Roles: Niki Sanders and Tracy Strauss

The most unkillable actress in the history of TV, Larter’s split personality character Niki was killed off, but then we learned she was actually a triplet, giving rise to Tracy.

The Cast, How I Met Your Mother
Roles: The original and doppelganger characters played by Alyson Hannigan, Cobie Smulders, Jason Segel and Josh Radnor

On HIMYM the characters all have doppelgangers, identical look-alikes wandering the city. There’s Stripper Lily, Lesbian Robin, Mustache Marshall and Mexican Wrestler Ted.

S. Epatha Merkerson, Law and Order
Roles: Denise Winters and Lt. Van Buren

Law and Order lasted so long that it was inevitable that some actors would show up more than once as different characters. But the most memorable instance was Merkerson, who showed up as a cleaning lady whose son was murdered in season 1 before starting her 17 seasons as a series regular.

Terry O’Quinn, Lost
Roles: John Locke and the Man in Black

John Locke was a fascinating and enigmatic figure who confused fans with his resurrection in season 5, until the end of the season when we learned that he wasn’t Locke but rather the infamous Smoke Monster posing as Locke.

Martin Lawrence, Martin
Roles: Martin Payne, Sheneneh Jenkins and More

Martin Lawrence wasn’t just the star, he was nearly the entire supporting cast. Other than the leading role, Lawrence also played Sheneneh, an obnoxious stereotypical girl from the ghetto. Other more minor roles played by Lawrence are his own mother, Otis the security guard, Jerome the pimp, Roscoe the 10-year-old boy, Dragonfly Jones the weak martial artist, Bob the white surfer dude, Elroy the former musician and King Beef the blaxploitation movie star.

Harry Morgan, M*A*S*H
Roles: Major General Bertford Hamilton and Colonel Sherman Potter

Morgan earned an Emmy nomination for his guest performance as Maj. Gen. Hamilton in season 3, so they brought him back in a new role for season 4, where he proceeded to earn eight more Emmy nominations as Colonel Potter.

Jon Lovitz, Newsradio
Roles: Fred, Mike Johnson and Max Lewis

First he was a psych patient locked up with Phil Hartman’s Bill McNeal. Then he was a man threatening to jump off the building. Finally, after Hartman’s death, he was brought in a third time as a series regular to be the new voice of WNYX.

Patty Duke, The Patty Duke Show
Roles: Patty Lane and Cathy Lane

Back in the 1960s, Patty Duke played cousins (identical cousins all the way!) using old-school split screen technology and body doubles with wigs.

Diane Delano and Leslie Grossman, Popular
Roles: Delano played Bobbi Glass, Jessi Glass, Rock Glass and Uncle Tipton; Grossman played Mary Cherry and Baby Honeychild

On this other Ryan Murphy show about high school, Delano played ruthless science teacher Bobbi Glass and her whole family, from her twin sister, the school nurse, to her rich uncle. Meanwhile, Grossman played the wildly exaggerated southern tart Mary Cherry and her long-lost gangsta twin Baby Honeychild (aka B.Ho).

Aloma Wright, Scrubs
Roles: Laverne Roberts and Shirley

Nurse Laverne was sadly killed off, but luckily for Wright the show brought in a new nurse named Shirley. That’s right, she played two nurses named Laverne and Shirley.

Sheryl Lee, Twin Peaks
Roles: Laura Palmer and Maddy Ferguson

Lee played the infamous Laura Palmer, the character whose death was the initial catalyst in David Lynch's cult series, and then later played the part of Laura's cousin, Maddy Ferguson. The dark hair and glasses weren't fooling us, but the kind people of Twin Peaks seemed satisfied that these gals just shared a familial resemblance.

Nina Dobrev, The Vampire Diaries
Roles: Elena Gilbert and Katherine Pierce

Dobrev plays a modern girl who falls in love with a vampire and her own evil vampire ancestor who originally turned Elena’s boyfriend, Stefan, into a vampire. It’s a complicated love triangle when the two girls look the same.

James Jordan, Veronica Mars
Roles: Lucky and Tim Foyle

Jordan first showed up as the sexually-abused janitor of Neptune High and the actor was so well-liked that they brought him back the next season as TA Tim Foyle, the appropriately named foil for Veronica.

Seriosuly. It's like EVERYONE in cast plays two completly different characters! And I hope we will se yellow world soon too.. so.. even more characters. XD lol

^I agree. Watching most of the actors playing two completely different roles at once has been extremely fascinating. :D

I don't see any contest here.

i love love love lisa kudrow:)

I was gunna pick Fringe because they are EPIC actors who keep getting overlooked come awards season (GIVE JOHN NOBLE SOME BLOODY LOVE! But im sorry i love Phoebe and Ursula!

She's amazing!

I love Lisa Kudrow.. and Phoebe Buffay is my favourite TV character EVER, but I'm not big on the whole Ursula thing, so my vote goes to Buffy.

I thought Jeffrey Tambor's George/Oscar thing was hilarious, but the Locke/Flocke thing was done so perfectly, I had to pick it. =D

Nina Dobrev is awesome in TVD . She makes an amazing job !

lol Buffy Bot, and i never realised james jordan from vm played two characters

DEFINITELY. Just WOW.
I'm sure Fringe is amazing too, just need to catch up on that.

OH & Nina has improved a lot. :)

AMAZING.

I think all of them made a great job (and I don't say that too often)

omg the Buffy bot classic

& Fringe cast :D

Anna Torv and John Noble are beyond brilliant at playing their characters! Second would definitely be the cylons in Battlestar Galactica.

& Kudrow.

:)

I love the HIMYM one but this 'cause I never knew until now they were the same person.

The Buffybot was strange, but i kinda liked her. Sarah did something way different than her Buffy character. She did a great job! I LOVE YOU SARAH<3

Also like/love The Cast (Fringe), Lisa Kudrow (Friends), Jennifer Garner (Alias), The Cylons (Battlestar Galactica) and Aloma Wright (Scrubs).