Dean Cain (Dr. Curtis Knox) previously played Clark Kent / Superman in Lois & Clark: The New Adventures of Superman (1993).
Vandal Savage is the antagonist in the first season of the series DC's Legends of Tomorrow (2016). In the episode "Night of the Hawk (2016)", he uses the alias "Dr. Curtis Knox".
At the end there is a PSA for the Christopher and Dana Reeve Foundation starring Dean Cain.
Dean Cain plays Curtis Knox, who is a version of the comics villain Vandal Savage. Phil Morris, who plays the Martian Manhunter voices Savage in the Justice League and Justice League Unlimited cartoon series
In the opening teaser, the villain in this episode, Dr. Curtis Knox (Dean Cain) ethers his first victim, Sasha Woodman, with a handkerchief with his initials C.K. embroidered on it. This is a reference to his former role as Clark Kent in Lois & Clark: The New Adventures of Superman (1993), who has the same initials.