“Arrow” Season 5 is going to achieve a major milestone. The CW drama will hit 100 episodes this year, and it looks like plenty of familiar faces are returning for the big celebration. Not only is the hour going to take place within the epic four-show crossover, but “Arrow” will be bringing back some actors from the early seasons.

Stephen Amell, who plays the Green Arrow, revealed on Twitter that Deathstroke is on set. He’s in a full suit, so it isn’t clear if Manu Bennet is still the man behind the mask in Season 5, episode 8. However, it’s a nice surprise to see the character. Producer Mark Guggenheim claimed earlier this year on Tumblr that another DC project was preventing the show from bringing him back. It seems something changed.

Much like the Flash and Amanda Palmer, there will be both big and small screen versions of the character. Joe Manganiello will play the villain in Ben Affleck’s solo “Batman” movie.

Deathstroke, however, already has a long history on “Arrow” that stretches back to Season 2, and he isn’t the only character from Oliver’s pre-vigilante days appearing. Oliver’s father will also return.

Guggenheim revealed on Twitter last week that Jamey Sheridan would guest star in the episode as Robert Queen. Of course, Oliver’s father died during the accident that left Oliver on the island of Lian Yu. However, the producer noted that Robert’s appearance had nothing to do with flashbacks or Flashpoint (an alternate universe created on “The Flash,” which will affect “Arrow” in other ways).

Laurel (Katie Cassidy) will appear as well, despite her character Laurel being killed off last season. That actually isn’t too surprising since Cassidy signed a deal to be a series regular across all the CW’s DC TV shows. The actress posted on Facebook to reveal her involvement in the 100th episode.

Expect plenty of other guest stars since the milestone episode will be part of the highly anticipated four-show crossover. It still isn’t exactly clear who will be on “Arrow,” but Amell confirmed Sara’s (Caity Lotz) appearance.

With White Canary hanging out, it seems likely that the “DC’s Legends of Tomorrow” crew will be around. Perhaps the time travelers are to blame for all of the familiar faces coming back.

“Arrow” Season 5 premieres Wednesday, Oct. 5, at 8 p.m. EDT on The CW. The 100th episode will air in late fall.

Arrow Season 5 episode 8 Oliver (Stephen Amell) will revisit old friends and enemies in the 100th episode of “Arrow.” Photo: CW