Ava [Hunted] was that one comatose chick, Sara Conroy [Slumber] (and was also on Earthsea with Lana)
Dr. Waxler [Hunted] was James Beale [Nicodemus] AND Dr. Groll [Arrow, Fallout]
Duane Tanner [Croatoan] was Josh Greenfield [Krypto]
Jake Tanner [Croatoan] was Zack Greenfield [Krypto...go figure]
Robert Johnson’s Ghost [Crossroad Blues] AND Taylor [Hookman] was Mindy [Truth] AND Katherine [Cyborg]
Johnson’s Demon-girl (again? credited…) [Crossroad Blues] was a doctor [Jitters]
Ellen Harvel was Warden Anita Stone [Scare]
Teresa Ellis [No Exit] was Mary – Cheerleader [Devoted] AND Girl in Red Top [Unsafe]
Store Clerk [Simon Said] was *crazy* Mike the Bartender [Suspect]
Webber/Ansem Weems [Simon Said] was Luke [Asylum] AND Bronson [Static]
Mom (I guess the other Webber’s?) [Simon Said] was an officer [Recruit]
Angela [Children Shouldn't Play With Dead Things] was Kyla Willowbrook [Skinwalker] (I KNEW she looked familiar!)
Dr. Mason [Children Shouldn't Play With Dead Things] was John Frankle [Crush, Dichotic]
Matt [Children Shouldn't Play With Dead Things] was Nate [Façade, Devoted]
Lindsey [Children Shouldn't Play With Dead Things] was *blank* [Spirit] AND Gretchen Winters [Tomb]
Some other vampire (I guess) on Supernatural [Bloodlust] was Hank Richards [Reaper]
Orderly [In My Time of Dying] was an FBI Agent [Legacy, Covenant]
Dying Nurse [In My Time of Dying] was Becky [Wither]
Daniel Elkins [Dead Man's Blood] was the prison doctor [Transference]
Isaiah Mercant [Provenance] was Jonah Doyle [Truth]
Mark [Provenance] was Wingate Owner [Exposed]
Melanie Merchant (aka homicidal little girl) [Provenance] was Emily Eve Dinsmore [Accelerate]
Ann [Provenance] was Gia [Fade]
James [Hell House] was Coop [Recruit]
Sheriff [Hell House] was a Belle Reve Guard [Mortal]
Mordechai Murdoch [Hell House] was…someone… [Witness]
Landlady [Shadow] was Dr. Claire Foster [Perry, Shattered, Asylum]
Meredith Mcdonell [Shadow] was Brianna [Spell]
Jared Bender [The Benders] has done stunts
Lee Bender [The Benders] was a jail deputy [Heat]
A policeman [Nightmare] was a security guard [Mercy]
Cyrus Dorian [Route 666] was Bill Ross [Unaired Pilot, Pilot]
Jimmy Anderson [Route 666] was Dale Ross [Unaired Pilot, Pilot] AND Store Owner [Krypto]
Mrs. Rourke [Faith] was Mrs. Taylor [Truth]
David Wright (aka Parking Lot Protestor)[Faith] was a scientist [Hypnotic]
Some random dude [Faith] was Jack [Witness] AND…another random dude [Exposed]
Jason ? [Faith] was Agent Stocker [Gone] AND a doctor [Thirst]
Doctor woman [Faith] was a nurse [Reaper]
Rev. Roy LeGrange [Faith] was Mr. Summers [Leech]
Harley Jorgenson [Scarecrow] was Lawrence Grady [Blank]
College Professor [Scarecrow] was Mayor Tate [Ryan, Relic]
Holly [Scarecrow] was Madeleine [Spell]
Stacey Jorgenson [Scarecrow] was Mrs. Summers [Leech]
The bus station clerk [Scarecrow] was a DNA doctor [Lineage]
Sheriff [Scarecrow] was a soldier with the megaphone [Commencement]
Steve (husband guy in restaurant) [Scarecrow] was Wagner [Sneeze]
Emily [Scarecrow] was Jenna Barnum [Cool]
Kathryn [Asylum] was Buffy Sanders [Thirst]
Walter Kelly [Asylum] was Lachlan Luthor [Relic]
Dr. James Ellicot [Asylum] was Dr. Christopher Wells [Crush]
Mr. Guenther [Home] was a LuthorCorp employee [Tempest] AND Chloe’s Father’s friend [Truth]
Another random dude [Bugs] was Mr. Woodward [Memoria]
Dustin [Bugs] was an assassin [Shattered]
Lynda Bloome [Bugs] was Dr. Pamela Black [Rage]
Joanie [Bugs] was Naomi Van Horn [Fragile]
Travis Wheeler [Bugs] was Louis Leery, Jr. [Exile]
Cute Librarian [Hookman] was Dr. McCann [Lexmas]
Sheriff [Hookman] was Jim Gage [Hourglass]
Anchorman [Skin] was another anchorman [Reckoning]
A bystander [Skin] was I guess…another bystander [Aqua]
Zach [Skin] was some dude [Solitude]
Jessica was Kara/Lindsay Harrison [Covenant] (aka: Supergirl…since Supergirl is Kara…)
Jill [Bloody Mary] was Felice Chandler [Drone] AND Rhonda [Devoted]
Jack Lambert (aka: surviving pilot) [Phantom Traveler] was the Vice Principal [Red]
Max Jaffe [Phantom Traveler] was Jeff Palmer [Shimmer]
A waitress [Dead in the Water] was a student [Forever] AND…I guess…another student [Thirst]
Gary [Wendigo] was a frat cowboy [Thirst]
Roy [Wendigo] was Tyler McKnight [Fragile]

btw, i am not talented or patient enough to make up this list. i found it [url=http://community.livejournal.com/acklesaholics/164286.html#cutid1]here[/url]

I did a little Googling and found that the girl playing Supergirl on Smallville (Laura Vandervoort) is from Canada. LoL.