The CBS "Supergirl" TV series pilot episode is now being filmed and "Arrow" star Stephen Amell has been allegedly seen at the set which may indicate that he is going to appear on the pilot episode.

Comic Central City has reported that Stephen Amell of CW's "Arrow" has was spotted during the filming of the CBS "Supergirl" TV series pilot episode.

"Onlookers at the set of Supergirl claimed that they saw Stephen Amell there. Now while they just saw Stephen there, some have claimed that he was actually in his Arrow costume which means that Oliver Queen would appear on Supergirl," wrote Comic Central City.

It should be noted that Stephen Amell has posted on Facebook regarding CBS' "Supergirl" TV series recently.

The report by Comic Central City echoes the report of Entertainment Weekly, wherein Greg Berlanti has admitted that the "Supergirl" TV series actually exists in the CW universe where "Arrow" and "The Flash" resides.

"The show will follow 24-year-old Kara Zor-El, Superman's cousin, and with a twist that that could melt fanboy brains, Berlanti says it's possible this Supergirl could enter the worlds of Arrow and The Flash," wrote Entertainment Weekly.

Meanwhile, Comicbook.com has reported that the main villain for the season one of CBS' "Supergirl" TV series has been cast.

"Faran Tahir, recognizable to fans of Iron Man and Star Trek, has joined the cast of CBS' in-production Supergirl pilot, ComicBook.com has learned," wrote ComicBook.com

Comicbook.com then continued, "Tahir is playing The Commander, an alien military expert leading the forces aligned against Supergirl."