According to Arrow co-creator Marc Guggenheim, not a single actor approached to guest star in the show's finale turned down the offer to be involved with the series finale. Although there were some actors that ultimately weren't able to participate, everyone at least wanted to be part of it.
"There were a variety of different actors from the life of the show who we wanted to see return for the finale and we simply couldn't manage it, because -- it's funny. No one turned us down. Every person who we approached who wasn't in the finale was doing either another television show, ironically, or a movie," Guggenheim told Fake Nerd Podcast. "Even people doing television shows, it was tricky to get them. For example, Katrina Law is a series regular on Hawaii Five-0 and that production moved heaven and Earth for her to be part of Oliver's funeral, which the scheduling was so tight on that, we actually shot the first half of the funeral without Katrina. Katrina was headed from the airport to hair and makeup while we were shooting half that scene."
Guggenheim detailed how involving both Melissa Benoist and Grant Gustin -- who play Supergirl and the Flash, respectively -- was also an incredible scheduling challenge for the production, as they both had their own shows. He noted how the Arrow production managed to pull off "more miracles than I expected" in gathering everyone together for the finale. Given the monumental effort needed, Guggenheim unsurprisingly admitted he was burned out by the end, crediting Arrow's co-showrunner Beth Schwartz for stepping in and helping to pull everyone together.
"Even Melissa [Benoist] and Grant [Gustin] 's involvement was really, really challenging from a scheduling perspective, because they both have their own shows as well. We pulled off as many miracles as we could. I would say we ended up pulling off more miracles than I expected, and I really have to give props to Beth Schwartz. By the time 'Crisis' was done, I was so burnt out and I was particularly burnt out on the subject of dealing with actor schedules and dealing with agents and managers. Every single one of the cameos and guest stars in 'Crisis' involved at least several phone calls on my part alone, and I was so tired. So Beth really stepped up to the plate and did all that diplomacy. There's a lot of diplomatic work that goes into these sorts of things. She carried the water when I was way too tired to do so."
Arrow stars Stephen Amell as Oliver Queen, David Ramsey as John Diggle, Rick Gonzalez as Wild Dog, Juliana Harkavy as Black Canary, Katie Cassidy as Black Siren, Katherine McNamara as Mia Smoak, Joseph David-Jones as Connor Hawke and Ben Lewis as William Clayton-Queen.