"Arrow" showrunner Marc Guggenheim has shared a very interesting clue from "Arrow's" 100th episode table read. The tweet featured an image of various "Arrow" cast members, including Stephen Amell, Emily Bett Rickards, Willa Holland, Echo Kellum, newcomers Rick Gonzalez and Joe Dinico, and a surprisingly familiar face: Jamey Sheridan.

Sheridan played Robert Queen in "Arrow's" first season, which leads us to wonder: what could bring him back for Season Five?

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There are two obvious choices for Sheridan's return for the 100th episode. One would be a flashback scene with Oliver, perhaps a previously unseen moment from the boat crash. The second choice would be that due to Barry changing the timeline on "The Flash," Robert Queen survived and Oliver did not. This would allow Robert Queen to take on the Thomas Wayne/Batman role from the "Flashpoint" comic.

Unfortunately, Guggenheim debunked both of these theories in the text of his tweet saying: "No Flashpoint. No Flashbacks."

Arrow 100th Episode Table Read. No Flashpoint. No flashbacks. pic.twitter.com/bs4KXiPVNx

— Marc Guggenheim (@mguggenheim) September 23, 2016

If Robert is not appearing in a pre-island flashback, and he's not alive due to the alternate timeline of Flashpoint, we can think of two other possibilites. Oliver could be hallucinating Robert (which would not be uncommon for "Arrow,"), or he could be Earth-2's Robert Queen. "The Flash" has already established that Robert survived the sinking of the Queen's Gambit on Earth-2 via a news report which stated that the Earth-2 Green Arrow had been unmasked as Robert Queen, who took up the vigilante mask after the death of his son Oliver.

With Oliver firmly entrenched as Earth-1's Green Arrow, and his father portraying Earth-2's Green Arrow, the anniversary episode would make the perfect place for an epic father/son Green Arrow team-up. "Arrow's" 100th episode is also part of the planned four-part crossover between "The Flash," "Supergirl," "Arrow," and "Legends of Tomorrow," so anything could happen, especially with both Earth-2 and Flashpoint in the mix.

"Arrow" Season Five premieres on October 5; the 100th episode airs in December.