Lucifer season 2 may have predicted the Arrowverse's Crisis On Infinite Earths back in 2016, although that seems to contradict when the Devil's appearance in the mega-crossover is said to take place. Premiering in January 2016, Lucifer is about the titular Devil, Lucifer Morningstar (Tom Ellis), who abandoned Hell to run a high-end nightclub in Los Angeles. He then becomes the crime-solving partner of LAPD Homicide Detective Chloe Decker (Lauren German). Lucifer aired for three seasons on FOX before it was canceled and picked up by Netflix. The first half of Lucifer season 5 is set to premiere on the streaming service in August 2020.
Airing in December 2019 and concluding in January 2020, Crisis On Infinite Earths destroyed and rebirthed the Multiverse of The CW's the Arrowverse. Taking place across Batwoman, Supergirl, The Flash, Arrow, and DC's Legends of Tomorrow, the superheroes of the Arrowverse battled the Anti-Monitor (LaMonica Garrett), eventually defeating the cosmic tyrant. Crisis also established that Lucifer is part of the Arrowverse's overall Multiverse. The former Lord of Hell personally cameoed in The Flash's "Part 3," when John Constantine (Matt Ryan), John Diggle (David Ramsey), and Mia Smoak (Katherine McNamara) dropped by Lucifer's nightclub, Lux, looking for the Devil's help.
However, a throwaway line in Lucifer season 2 seemed to predict the Crisis. In the third episode of Lucifer season 2, "Sin-Eater," the Devil and Chloe Decker track a serial killer (Robin Givens) who tortured her victims. Back at the precinct, as Lucifer and Chloe worked the case, a website popped up on her computer screen threatening Judgment Day. This made Lucifer remark, "Judgment Day? Those people should really be careful how they use that phrase. It isn't actually due for another couple of years." As it turns out, "Sin-Eater" aired in October 2016, three years before Crisis On Infinite Earths, which was effectively the Arrowverse's Judgment Day. Did Lucifer inadvertently predict the end of the Arrowverse?
While it seems like Lucifer managed an eerie bit of soothsaying, the matter of when Lucifer's actual cameo in Crisis took place complicates things. Tom Ellis stated that his meeting with Constantine, Diggle, and Mia happened earlier in Lucifer's timeline, before the events of his series. Ellis told Entertainment Tonight, "We’re playing it as if it’s in the five years before the show, Lucifer, started, so when Lucifer spent five years in LA before meeting the detective and all those things unfolding."
Although this makes sense within the context of Crisis, it also means that every season of Lucifer now takes place in the Arrowverse's future. Yet, Ellis' explanation doesn't entirely mesh with what's seen in Lucifer; if the whole series is set in the future, fashion and technology don't appear to be at least five years advanced. Fans watching Lucifer all along never got the impression that the series was set in the future. Then again, Lucifer is set in its own Earth within the Multiverse and the rules could simply be different on the world the Devil calls home. However, it could also be true that Ellis' explanation was merely an expedient way to explain Lucifer's cameo, but it may not necessarily hold as canon.
Regardless, Lucifer's appearance in Crisis was a great treat for fans, even if it is a bit problematic logically. Still, it would make more sense that Lucifer has been happening in real-time all along, just like the Arrowverse shows are, and the Devil (who would be aware of cosmic happenings) had foreknowledge of Judgment Day, a.k.a. Crisis On Infinite Earths, way back in Lucifer season 2.
Lucifer season 5 will be available to stream on Netflix on August 21, 2020.