The Season 5 finale of Arrow will see the return of many characters, including Deathstroke, Nyssa al Ghul, Digger Harkness and more. However, there seems to be one more surprise guest set to appear in the season's final episode, "Lian Yu."RELATED: The CW Release Fall Season Synopses for Arrow, Flash, Supergirl and MoreAccording to the Emerald Archer himself, Stephen Amell's "favorite cameo" has yet to be revealed. It's currently unknown whether this character will appear via flashbacks or participate in the fight against Adrian Chase. Although there are a ton of possibilities to speculate, Amell at least teases that the cameo is someone who has been on the show previously."My favorite cameo in the Arrow Season Finale is not featured in any of the previews," Amell said on Twitter. "Love this person so much for coming back."

Could we see the return of former sidekick Roy Harper or Oliver's mother Moira Queen? Perhaps a superhero crossover from The Flash, Supergirl or Legends of Tomorrow is more likely. The conclusion of Season 5 will air May 24, featuring the final showdown between the Green Arrow and Prometheus.

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Airing Wednesdays at 8 p.m. ET/PT on The CW, Arrow stars Stephen Amellm Emily Bett Rickards, David Ramsey, John Barrowman, Willa Holland, Paul Blackthorne and Echo Kellum.