Trivia

She is a skilled guitarist and pianist.

She lost a significant amount of weight during the production of Arrow Season 2, to better convey Laurel's addictions to painkillers and alcohol. The following season, she bulked up in the gym as Laurel suited up as Black Canary.

Jesse McCartney wrote his songs "Tell Her", "She's No You", and "Bleeding Love" (last one sung by Leona Lewis) for Katie.

Has remained close with her Supernatural (2005) co-stars, Jared Padalecki and Jensen Ackles.

Reportedly cried when she first put on Sara Lance/the Canary's black jacket in early production of Arrow (2012), before her character of Laurel Lance took the Black Canary mantle.

Started off her career modeling with Abercrombie and Fitch.

Has starred in three horror movie remakes When a Stranger Calls (2006), Black Christmas (2006), and A Nightmare on Elm Street (2010).

Katie is named after Katharine Hepburn; also, one of her two middle names is taken from Evelyn Ward - Katie's paternal grandmother.

Daughter of David Cassidy and Sherry Williams. Granddaughter of Jack Cassidy and Evelyn Ward. Half-sister of Beau Cassidy. Former stepdaughter of Sue Shifrin.

She stands an inch taller than her father, David Cassidy, who died four days before Katie's 31st birthday.

She has played the same character (Laurel Lance / Black Canary) in three different series: Arrow (2012), The Flash (2014) and DC's Legends of Tomorrow (2016).

Did a cover of her father's song, "I Think I Love You".

Is roommates with, former Arrow cast-mate, Caity Lotz.

Stars as DC Comics icon Dinah Laurel Lance/Black Canary/Black Siren on Arrow (2012). In real life, she went to prom with Tyler Hoechlin who portrayed Clark Kent/Superman in Supergirl (2015).

Participated in the creation of Laurel Lance's Black Canary costume seen on Arrow (2012).

Co-created a fashion blog called Tomboy KC and co-designed an eyewear line for Glasses.com.

Bradley Hargreaves, drummer for Third Eye Blind, is Katie's brother-in-law.

Did not meet her biological father David Cassidy until she was in the fourth grade.

Due to her recurring roles in horror films she is regarded as a modern day "scream queen".

Was going to appear in a 2007 remake of Revenge of the Nerds (1984) starring Adam Brody but after three weeks of filming the project was canceled.

Half-Niece of Shaun Cassidy, Patrick Cassidy, and Ryan Cassidy, the sons of her grandfather's marriage to Shirley Jones.

She has English, German, and Irish ancestry on both sides of her family; along with Swiss on her father's side.

She was a cheerleader in high school.

She is a fan of the Seattle Seahawks NFL team.

(January 8, 2020) Filed for divorce from her husband of 13 months Matthew Rodgers.

Shares her birthday with half-cousin Caitlin Cassidy, who is exactly 5 years older.

Though Laurel is meant to be a couple of years older than Sara on Arrow (2012), Katie is only about a month older than Caity Lotz.

One of three Supernatural (2005) guest stars linked to the role of the iconic DC heroine Black Canary. Alaina Huffman portrayed Dinah Lance on Smallville (2001), while Alona Tal has been strongly rumored for the role in the DC Extended Universe.

She does her own singing in the movie, Cover Versions (2018).

On June 5, 2017, Cassidy announced her engagement to Matthew Rodgers. They have been in a relationship for a year.

Half-cousin of John Cassidy, and Jack Cassidy.