Possible spoilers, I guess.
So anyone who's read the comics remembers the twins (Allen and Donna's kids) Ben and Billy, who, after their parents' deaths became adopted by Andrea and Dale. One of the twins (I can't remember which one was which for the life of me) went kinda psycho and killed the other one, then was later killed by Carl.
I have a theory about Lizzie and Mika (the two sisters in the tv series):
I believe that Lizzie was the one feeding the walkers (as we saw, she seems to have a peculiar facination with them - treating them almost as pets at times). As we saw in "Too Far Gone", Tyreese discovered a gruesome whateverthehellthatwas, which he believed was made by Karen and David's killer/ whoever was feeding the walkers. Now, seeing as Carol isn't the type of person to gut a rat to make a dream catcher, I believe that it's highly likely it was Lizzie who killed Karen and David. Maybe she saw it as "being strong" for the group, as Carol had taught her to.I think Carol took the fall for her, because she sees herself as Lizzie's "new mom", and wanted to protect her.
Now, with Tyreese (who's still hell-bent on finding Karen's killer) staying with Lizzie and Mika after the prison assault, here are some predictions I've had:
Lizzie may go crazy and kill her sister (just like when one of the twins in the comics killed the other one)
Tyreese may find out that Lizzie killed Karen and David and who knows what he might do (seeing his rage when he found Karen dead, but then taking into account that he probably wouldn't kill a kid leaves for an interesting moral dilemma).
Just a thought, does anyone else think this is possible??