Crisis on Earth-Three

"Crisis on Earth-Three" 1 is the fifth annual DC Television Universe crossover event, featuring episodes of the live-action television series Wonder Woman, Superman , and Batman on NBC. The crossover began on November 20, 2017, with Wonder Woman, continuing on November 21, 2017, with Superman, and concluded on November 22, with Batman. In "Crisis on Earth-Three", Clark Kent and Lois Lane's wedding brings all their closest friends and allies to Metropolis, where they are shocked when they learn of "Earth-3", a parallel universe where evil versions of themselves exist.

Development for a crossover of the three series, and at the time with The Outsiders as well, began in November 2016 after the release of the previous crossover, "Heroes United". When The Outsiders was announced to premiere mid-season, thus giving it no time to resolve its cliffhanger, the crossover was backed down to three series, though cast members from The Outsiders were able to make appearances. The premise and title of the crossover were revealed in September 2017 as production on the episodes began. A subsequent crossover aired the following year, titled "Brainiac".

1 It is written as "Earth-Three" in the title, though in the series it is written as Earth-3.

Plot
In Metropolis, Clark Kent awakens early in the morning and leaves, as it "is bad luck to see the bride before the wedding". In Washington D.C., Diana Prince and her team (Steve Trevor, Dale Gunn, Ray Palmer, and Donna Troy) take down Amazo, and Etta Candy reminds them of Clark and Lois's wedding that afternoon. In Gotham City, the Bat Family (Bruce Wayne, Barbara Gordon, Selina Kyle, Kate Kane, Luke Fox, and J'onn J'onzz) breaks up a gang fight, while Jim Gordon also reminds them of the wedding. Later that day, Clark and his groomsmen, Bruce, Steve, and Jimmy, and Lois and her bridesmaids, Lucy, Diana, and Kara, go through the rehearsal, and at dinner that night, Selina ends up with the bouquet, indicating she will get married next. At the actual wedding, just before Clark and Lois give their vows, a portal opens and "Owlman" leads an army of armed soldiers. Bruce believes it is Lincoln March at first and the heroes are able to take him on, until Bruce takes off Owlman's mask and he is revealed to look exactly like Bruce. Through the portal, two individuals who look exactly like Clark and Lois, though the latter with abilities, appear and free "Bruce" and they take the real Clark and Lois through the portal. The remaining heroes, left in shambles try to figure out what happened, and J'onn reveals that there are actually an infinite numbers of earths, each with a different history, and those they saw were from Earth-3. Diana, Steve, Kara, Bruce, and J'onn are able to open a portal and travel to Earth-3, which they find a dark dystopia, with the "Crime Syndicate" having taken over.

In New Gotham on Earth-3, the heroes split up: Bruce and Diana go to Wayne Empires, the Crime Syndicate's base, while Steve, Kara, and J'onn try to seek out the heroes of the Earth. The latter group travels to Metropolis and discovers a Resistance, led by this Earth's Diana and Lex Luthor, and also including Dale Gunn, Harper Row, and Dick Grayson. Diana is shocked to see Steve alive, until she realizes he is from another Earth. Kara learns she was never found on this Earth, and J'onn's whereabouts are unknown. The Earth-1 heroes explain themselves and agree to help Diana and Lex reclaim the Earth. At Wayne Empires, Bruce is recognized as his doppelganger in a face detection and they are able to take the elevator to the bottom floor. However, security there recognizes Diana as her "fugitive" self and attack her. They easily defeat the security and find the archives there, which reveal that Thomas Wayne Jr. killed his parents and became Owlman, Clark Luthor was found by the Luthors as a child and raised to be the terrorist Ultraman, and Lois Lane soon met him and became Superwoman. Other enemies on their side include Renee Montoya and Black Beetle. When the Crime Syndicate find them, Bruce and Diana narrowly escape, and are found by the Resistance, where Lex reveals they have a mole on the Crime Syndicate. Meanwhile, on Earth-1, Waller sends Lucy, Conner, Luke, and Selina to find more materials to build a "breach device" to travel Earths.

Clark and Lois attempt to laugh about their terrible wedding day, while Bruce, Diana-1, Lex, and Kara break in and rescue them. Superwoman arrives and reveals she is the mole and kisses Lex, revealing she is actually Lois Luthor, his wife. The group makes it out of Wayne Empires barely and they return to the Resistance. However, the Crime Syndicate has their own mole, Dick, who sets off a bomb, killing almost all of the remaining Resistance, including Diana-3. Harper, Steve, and J'onn rendezvous with the rescue team and inform them of what happened. They travel back to Earth-1, where the heroes there are shocked by Lex's surprising turn. They try to come up with a plan, when suddenly several portals in downtown Metropolis open and the Crime Syndicate and their armies arrive to take over. The heroes unite together downtown and face the armies. Clark-3 and Thomas try to convince Lois to rejoin them, but she easily knocks down both of them. Kate tries to convince Renee that she is being opressed, and she reveals her true feelings about the Crime Syndicate, turning on them. Soon, Black Beetle, Ultraman, and Owlman are stopped and the army retreats. Lex learns there are more rebels everywhere and returns with Lois, Harper, Renee, and a newfound hope. Clark and Lois have their real wedding, while Bruce proposes to Selina, who says yes.