Why it's possible:
- Wren seems to have a thing for younger girls, between his flings with Hanna and Spencer. He could have dated Ali, too.
- He starts working at Radley Sanitarium after Mona gets admitted for treatment.
- During one of her surreptitious visits to Aria, Ali specifically says, "I'm surprised Spencer hasn't figured that out." It might mean "A" is closer to Spencer than the rest of the girls, and Wren fits in with that logic.
- He's a doctor, giving him access to the drugs, medical records, and other supplies "A" seems to possess.
- This scene, where Wren is having a strange phone conversation and coloring in a drawing of what looks like Red Coat. His last words in the scene: "Just goes to show, you can't trust anyone."
Why it's not:
- During the Summer finale of season four, when the girls find the "A" lair, they find a picture of Wren with the note "Wren at Radley," meaning he's under the mystery villain's scrutiny.
- When Mona starts talking to him about trust and loyalties, he tells her he has no idea what she's talking about.
Source: ABC Family