Spoilers ahead for Arrow season 7.
Arrow season 7 premiered this week and introduced a surprise character - Oliver Queen's adult son 20 years in the future, played by actor Ben Lewis.
Lewis has now joined the cast of Arrow season 7 in a recurring role as the older William Clayton, according to Deadline. The younger version of Will has been played by Jack Moore since 2015. Lewis' scenes as Clayton in the Arrow season premiere took place 20 years in the future, adding a level of mystery to the years in between the two timelines.
Barry Allen's daughter from the future is a central character in Flash season 5 - though she has traveled back in time to the present day.
Arrow and Flash will crossover in December as part of CW's "Elseworlds" DC-TV event.