Credit: ABC Family

Pretty Little Liars isn't afraid to go big with its twists, so its fans are always thinking up crazy theories in an attempt to figure out what could happen next in Rosewood. Every week, we like to delve into those theories and pick out an intriguing one to explore.

This week, it's all about one of the most suspicious characters around: Ali's mom, Mrs. DiLaurentis. The Liars think Mrs. D might be "A", but what if she has a different secret… like having a twin sister? A lot of fans are starting to consider this a possibility.

Why would fans think Mrs. D has a twin? Here are some of the reasons!

Someone must have a twin, right? If you've somehow missed this tidbit, it's important to understanding where this theory comes from: In the Pretty Little Liars books, Alison has a twin, who ends up being the key to both her murder and to the second "A" who pops up after the original "A" (also Mona) is killed.  The writers and actors have all said that they aren't going to make Ali have a twin on the show. However, because the show has hinted at twins being important like with that creepy story Ali told in the first Halloween story about one twin attacking another many fans think a different character will turn out to have a twin.

Mrs. D has all those connections to Radley. If there is a secret twin involved in this show, that twin is probably crazy and/or evil. Why else have a secret twin? And if you live in Rosewood and are evil and/or crazy, you probably end up at Radley at some point. Mrs. D, of course, has all sorts of connections to Radley. She's on the Board! Could that be because her twin is hidden there? Or maybe she was the one who spent some time there, while her twin was out and about in the world...

If either of these scenarios are the case, it's possible that Mrs. D or her twin is the one who killed Toby's mom! We still have no other idea how that connects to anything.

Could the twin be connected to Sara Harvey? Some fans even think that Mrs. D's twin could be Sara Harvey's mother. After all, Sara was so much like Ali it's almost weird... unless they were actually related. And what if Sara is the one in Ali's grave? Mrs. D's twin would not like that. In fact, maybe it's actually the twin who is around and acting extra crazy right now... maybe because she realizes what actually went down.

What do you think of this theory — is it possible, or totally crazy? Sound off in the comments below.

Catch the next episode of Pretty Little Liars Season 4 on Tuesday, March 18, 2014 at 8 p.m. ET on ABC Family.

Rebecca Martin is an Associate Editor at Wetpaint Entertainment and our resident Game of Thrones, Breaking Bad, and genre TV expert. Follow her on Twitter and Google+!