throughout the series, oliver is joined by others in his quest, among them former soldier john diggle (david ramsey), i.t. expert and skilled hacker felicity smoak (emily bett rickards), former assassin sara lance (caity lotz), aspiring vigilante roy harper (colton haynes), oliver's sister thea (willa holland), and attorney-turned-vigilante laurel lance (katie cassidy). the group also receives support from laurel and sara's father, detective quentin lance (paul blackthorne). during the first five seasons of the show, characters from oliver's past appear in a separate story arc based on oliver's flashbacks, which highlight parallels from oliver's history that shape events in the main story. starting with season seven, a series of flash-forwards focus on oliver's children william and mia, exploring how present events would affect their future and green arrow's legacy.