Barry is attacked by the shark-man and is saved by Harrison Wells when Patty's gun is insufficient for the job in episode 2x04 "The Fury of Firestorm". The police fight against the meta-humans under Zoom's control in episode 2x22 "Invincible".
Cisco has a vision of birds crashing into the ground on Earth-2 in episode 2x22 "Invincible".
Diggle follows Moira to a covert meeting with Malcolm and overhears part of it in episode 1x13 "Betrayal".
Laurel rants about her father spying on her to Tommy who gets mad about her talking to The Vigilante in episode 1x13 "Betrayal".
Diggle finds one of the virus carriers at a downtown plaza who is then taken out by Thea in episode 3x23 "My Name Is Oliver Queen".
Chloe and Lucifer approach John Bryant who is photographing some celebrity in episode 1x02 "Lucifer, Stay. Good Devil.".