Board Shorts

Board Shorts formerly Beach Hottie, (but Emily and Hanna called him the "Beach Hottie in Board Shorts") had a relationship with Alison, according to CeCe Drake.

Identity and Relationship with Alison
In Emily's biology notebook, there was a conversation about Beach Hottie. Emily found out that Alison may have been pregnant with Beach Hottie's baby that summer in Cape May and that they had "done it without protection multiple times." Later, Mona said to Spencer that Alison wasn't pregnant and it was a false alarm.

Trivia

 * Detective Darren Wilden is one of the main suspects to be Alison's infamous "Beach Hottie" because he is aways "getting some" and has already been proven as suspicious throughout the past seasons. The Liars also found a photo of Detective Wilden and some of his friends in Cape May the same summer as Alison. However, he doesn't seem like the type to chase a high school girl, and the only thing that connects them is CeCe's word.
 * Noel Kahn, the famous party thrower, was vaguely spoken about from Alison. In a flashback from Spencer it is revealed that once the girls were by the lake and Noel was passing by with his girlfriend at that time and they were walking towards the Kissing Rock. Ali spies Aria checking Noel out and makes a comment on how "good he looks tanned."
 * Emily and Jason found a collage in Jason's Dad's new office with pictures of Ali from her summer in Cape May - One of which is her on a boat with Detective Darren Wilden and CeCe Drake. Ali signs the collage with XOXO, A. After getting the picture Jason is hurt and the picture is gone.
 * Some say that Board Shorts and the Beach Hottie are two different people.

Suspects
(By fans)

Current

 * Darren Wilden
 * Wren Kingston
 * Gabriel Holbrook

Eliminated

 * Ezra Fitz - Ezra said they "didn't do it" in the finale, the Beach Hottie and Ali had a sexual relationship with each other, but Beach Hottie and Board Shorts may be two different people.
 * Noel Kahn  - Noel is not old enough to be the "older guy" or "board shorts"