2) David Ayer Regulars
Just as Zack Snyder employed a number of Watchmen actors in BvS, David Ayer recruited a lot of his frequent collaborators to feature in Suicide Squad.
In particular, three veterans of 2014’s Fury appear – Jim Parrack (who played previously mentioned Mr. Frost), Kevin Vance and Scott Eastwood. Kenneth Choi also briefly turns up in Katana’s flashback, after working with the director in Street Kings. Plus, Corina Calderon plays El Diablo’s wife here and previously appeared in End of Watch. Speaking of that movie, at one point the Joker is firing a gold-plated gun – the same gun that appeared in End of Watch.
Harley Quinn’s choice of weapons are also of significance. Traditionally, Harley carries an oversized mallet – the same one she initially has at Belle Reve. Her later choice of baseball bat, meanwhile, comes from the 2015 video game Batman: Arkham Knight.