The latest updates and spoilers for "The Flash" Season 4 will feature a new change for Earth 2 Harrison Wells in the show, and a crossover starring Kid Flash and Citizen Steel.

A big change for Harry Wells

Executive producer Andrew Kreisberg teased an emotional journey for Harrison "Harry" Wells in the "The Flash" as the fourth season will explore the things that are still missing in his life despite having his daughter, Jesse and the owner of his Earth's S.T.A.R. Labs.

"He's a genius, and his daughter is safe, and she's The Flash on Earth-3, and he's one of those people who's realizing that he doesn't have a life," Kreisberg told Entertainment Weekly.

"So Season 4 for Harry is realizing what he's missing in his life and what he needs to become better, more complete person."

Tom Cavanagh stated at SDCC 2017 that Harry will be present in the first haft of season 4 as the show will introduce a new Harrison Wells from another earth. This new wells will bring something different to Team Flash in their fight against a new main villain, Clifford De Voe a.k.a. The Thinker.

Perhaps, the showrunners will introduce a new love interest for Harry in the show similar to H.R. Wells and Tracy Brand in season 3.

Character crossovers

The new DC Heroes TV trailer revealed an interesting scene that featured an interaction between Kid Flash and Citizen Steel, hinting a possible crossover episode.

It is unknown if the crossover will happen in "Legends of Tomorrow" or in "The Flash" TV series.

There have been many instances that "Arrowverse" characters guest starred in different DC TV shows in order to add more depth and importance for the episode's plot. Characters such as Felicity Smoak, John, and Layla Diggle were frequently featured in "The Flash," while Cisco Ramon and Caitlin Snow first appeared on "Arrow."

These small appearances also provide an introduction to new characters in the "Arrowverse" or plot details for future epic crossovers.

The CW Network announced the titles for the next "Arrowverse" crossover episodes and teased that heroes will face a threat far greater than the Dominators last year. The first episode will start with "Greater Foes" in "Supergirl" followed by "Greater Loss" on "Arrow, " then "Greater Threat" in "The Flash," and it ends in "Greater Menace" in "Legends of Tomorrow.

Fans have speculated that the new foes in the crossover could be the alien warlord Mongul and will likely bring his planet-sized battle station, Warworld to the "Arrowverse."