- In the book series, Alison's disappearance takes place the summer before the girls went into 8th grade, 3 years prior to the series beginning. In the T.V. show it only takes place 1 year earlier.
- Alexis Denisof was originally cast as Byron, but before the pilot was replaced by Chad Lowe.
- Jean Louisa Kelly was originally cast as Ella, but before the pilot was replaced by Holly Marie Combs.
- Many of the scenes were filmed on the same lot(s) used as the town of Stars Hollow from Gilmore Girls.
- Wren's last name was believed to be Kim before being stated as Kingston.
- Ashley Tisdale was offered an audition but didn't take it, and instead went to an audition for 'Hellcats' and got the role.
- Mona's surname was going to be spelled Vanderwall for the show but was changed back to Vanderwaal.
- The events of the pilot episode cover the entire first book in the Pretty Little Liars series.
- Filmed in Vancouver in the winter even though the episode was set in the summer. Even though they were wearing bikinis, they had to wear boots as the camera shot from the belly button up.
- Roark Critchlow who plays Tom Marin (Hanna's father) was on Days of our Lives as Mike Horton, Abigail Deveraux's uncle, who was played by Ashley Benson, though the two were not on the show at the same time.
- CAMEO(Sara Shepard): makes a brief appearance as Ms. Shepard, a teacher substituting for Ezra.
- The address of the creepy house is 313 Mockingbird and the name of the asylum car outside is Radley, both are in reference to "To Kill a Mockingbird" by Harper Lee.

