|Actor|| Elizabeth Marleau (3.10)|
Carrie Ann Fleming (5.15 and 7.10)
|Dates|| ???? (killed by Bobby while possessed by a demon)|
2005 (resurrected by Death as a zombie)
|Location||Sioux Falls, South Dakota|
|Episode(s)|| 3.10 Dream a Little Dream of Me|
5.15 Dead Men Don't Wear Plaid
7.10 Death's Door
8.16 Remember the Titans (mentioned)
I'm gonna go out on a limb here and say you've never been in love. He's my husband. My job is to bring him peace... not pain.
– Karen Singer, 5.15 Dead Men Don't Wear Plaid
Karen was married to Bobby Singer, and was described as the "the love of his life." At some point in the past, she was [[possessed] by a demon, and Bobby, unsure of what was happening stabbed her multiple times to effect. Rufus Turner arrived and exorcised the demon, leading to Karen's death.
Bobby becomes trapped in his subconscious by Jeremy Frost. He is haunted by the memory of his wife, who he killed when she was possessed, stabbing her when she tried to attack him. This was what propelled him into hunting, motivated by the desire to redeem his failure to save his wife due to his then-ignorance of exorcism techniques. She is not named in the episode.
Death comes to Bobby's town of Sioux Falls and raises the dead, including Karen, Bobby's dead wife. Having previously tested her after her return to confirm that she is not any kind of hostile being, Bobby tries to convince Sam and Dean to leave the town alone, as he wants to keeps his wife. But after she begins to turn, she begs Bobby to kill her before she hurts him. As her last act as herself, Karen warns Bobby that, because he's helping Sam say "no" to Lucifer, Death has his eye on him, and raising Karen was to punish Bobby. After her demise, Bobby notes that seeing her again and being forced to kill her made her death worse than it was before.
As he lies in a coma, Bobby's subconscious works out that a possible way to recover is to access his darkest memories. One of them occurred three days before Karen was possessed by a demon and he was forced to kill her. She wants to talk to Bobby, and during the conversation he reveals that he doesn't want to have children, something he has never shared with her. Karen is extremely distraught. Bobby reflects that what was worse than killing her, was knowing that they never got past this argument.
When feeling bored, Sam suggests that they investigate possible zombie activity in the form of a news report detailing how a car accident victim got up and walked away. Dean asks if there has been any reports of brain-munching, Sam citing Bobby's wife as an example of zombies that didn't eat people.
- Elizabeth Marleau who played Karen in 3.10 Dream a Little Dream of Me was unable to reprise the role for 5.15 Dead Men Don't Wear Plaid as she was very obviously pregnant at the time, and the production team thought a "pregnant zombie wife... would have been more than the episode could handle."S5Com
- Carrie Ann Fleming who took over the role, previously played the dying nurse in 2.01 In My Time of Dying.