* DawsonCasting: Weirdly inverted - Katie Cassidy (Trish) is four years younger than her character and Amber Borycki (Beth) is three years younger than hers. Played straight with several of the others though.
** Played doubly straight with Madison, which is one of the reasons her character is so Narmy. She was a twelve-year-old playing a nine-year-old, which wouldn't be so bad if her character ''acted'' nine years old. She comes off more like a twelve-year-old playing a nine-year-old playing a four-year-old.
* EnforcedMethodActing: Even though they knew it was coming, and they did multiple takes of it, when the seagull falls on the bridesmaids table during the first episode, their screams of fear were genuine. No matter how many times you drop a bird on their faces, they never get used to it.
* ExecutiveMeddling: [[spoiler:Madison's InfantImmortality]] aside, the [[http://popminute.com/news/?christopher-gorham-reveals-harpers-island-ending-1121 original ending]] featured [[spoiler:Henry getting away with it. He ends up with Abby and she never knows.]] The writers had to change it because the show needed a happy ending.
* FakeNationality: Averted with Cal, who is played by a British actor. Abby is played by Irish actress Elaine Cassidy.
* HeyItsThatGuy: Hey the British guy from Film/EpicMovie and the blonde chick from Film/OpenWater 2 are a dating in this show!
** [[Series/{{Supernatural}} Bobby]]/[[{{Series/Deadwood}} Ellsworth]] is Abby's dad, the sheriff on the island. Also [[Series/{{Supernatural}} Ruby]] is Trish Wellington, the bride to be.
** After recognising Callum Keith Rennie in the photos of Wakefield, anyone with even a passing familiarity of the kind of characters he specializes in will be sure of [[spoiler:the serial killer's return]] right from the start.
** Booth is also the host of ''GraveEncounters''.
** Then of course, you've got Ben Cotton (Shane), who's done a lot of stuff for the SyFy channel, with his most memorable role being Doctor Kavanagh from Series/StargateAtlantis.
** There's also Brandon [=McLaren=], the Red Ranger from Series/PowerRangersSPD, as Danny.
** [[RetroactiveRecognition He wasn't terribly big at the time,]] but hey, it's that guy who played [[UglyBetty another Henry]] and [[Series/{{Covert Affairs}} a blind guy!]]
** Maggie owns and operates a [[Series/OnceUponATime bed and breakfast]] alongside the Candlewick.
** Wow, [[Series/DesperateHouseWives Susan's ex husband, Carl]] is Mr. Wellington.
** And Abbey's dad is a [[Series/{{Supernatural}} paranormal hunter]]. And Trish is a demon.
* WhatCouldHaveBeen: The [[http://popminute.com/news/?christopher-gorham-reveals-harpers-island-ending-1121 original ending]].
* The actress who plays Abbey is good friends with ColdPlay. She even appears in the end of their music video for ''the scientist''.
* WordOfGod: The night a new episode airs, the actor who got killed off would take part in an online interview with fans, in a Q and A session about the show. Seeing as how none of the actors knew what happens in the show after their characters dies, and they weren't allowed to give away any spoilers, it was mostly just for clearing up misconceptions that were already supposed to be obvious.