HBO's Lanterns has slipped a significant DC Comics Easter egg into its third episode, potentially laying groundwork for a well-known Batman villain to enter James Gunn's rebooted DC Universe. During a flashback showing John Stewart's recruitment interview in an abandoned shopping mall, a sign for "Janus Cosmetics" appears in the background, a company with deep ties to Batman rogue Roman Sionis, better known as Black Mask.

In the comics, Janus Cosmetics is the Sionis family firm that Roman inherits and later ruins, prompting a bailout from Bruce Wayne that fuels his transformation into the crime lord Black Mask, first introduced in 1985. The name Janus, the two-faced Roman god of transitions, is also seen as a subtle nod to duality fitting the character. While this version of Black Mask previously appeared on screen in 2020's Birds of Prey, played by Ewan McGregor, that film belongs to the now-defunct DC Extended Universe and is not canon to the new continuity, meaning the sign only confirms the company's existence rather than the villain himself. Some fans have also speculated the reference could hint towards Clayface, another Batman villain reportedly due to debut later this year.