Trivia: The actor Ted Whittall, who took a small part in the film, portrayed Rick Flag in Smallville season 10.
Trivia: The first words that David Ayer said to Jai Courtney on set were "Embrace your inner shitbag."
Trivia: Amanda Waller operates out of the "John F. Ostrander Federal Building." John Ostrander is the comic book writer who reinvented the Suicide Squad using the concept of a supervillain team forced to do the government's bidding. The Suicide Squad title was originally a World War II comic, akin to the Dirty Dozen.
Trivia: Stay after the credits for another scene with Viola Davis.
Trivia: The footage of Harley and the Joker dancing is similar to Alex's Ross' art work from Harley Quinn #1.
Trivia: Fleetingly visible on screen among Harley Quinn's bio-data is the phrase "accomplice to the murder of Robin." In the comics, Jason Todd, the second Robin, was killed by the Joker - this took place before the character of Harley Quinn was created.
Trivia: While he's only referred to as "Rick Flag", the character is actually Rick Flag Jr. - in the original Suicide Squad comics, Rick Flag Sr. Was the leader of the first Suicide Squad, a Dirty Dozen-style commando team operating during World War II.
Answer: Because he's already been into the liquid, it's how he became the Joker. He wanted Harley to be just like him.