'Legends of Tomorrow': Who Is Wally West?

After being absent since the first hour of "Crisis on Earth-X," The Flash's Wally West came aboard the Waverider tonight on Legends of Tomorrow finally giving Kid Flash a place where he can grow into being a hero away from Barry Allen's shadow, Legends style.

Mild spoilers for tonight's episode of Legends of Tomorrow, "Here I Go Again", below!

In tonight's episode, Wally West (Keiynan Lonsdale) joins the Legends and he comes on board at an interesting time. The Legends are not only dealing with the growing threat of Mallus generally, a time loop specifically, but they are also still grieving both the loss of Martin Stein (Victor Garber) who died during "Crisis on Earth-X" and the absence of Jefferson Jackson (Franz Drameh) who departed the team following Martin's death. While having a new hero on the team to help fill the space left behind by the Stein/Jackson Firestorm duo is welcome, Wally's arrival is complicated the team's other newer arrival, Zari (Tala Ashe).

"You'll actually see Zari and Wally clash," Ashe told Collider. "By the end of Episode 3x11, Zari is like, 'Okay, these team members are my family.' and then this new guy comes in and it's like, 'Who is this guy?!' He's very over-eager, and he's shiny and happy, which is not Zari's vibe."

So, who is Wally West with his shiny and happy vibe? Here's what you need to know.

First appearing 1959's The Flash #110 Wally West is the nephew of Iris West, a young man who gets speedster powers in a freak accident not unlike the one that gave Barry Allen/The Flash his powers. With his own superpowers, Wally put on a version of The Flash costume and became Kid Flash, operating as the only superhero in his hometown of Blue Valley, Nebraska when he's not working with The Flash. Wally later becomes the Flash when Barry sacrificed himself to save the Earth in "Crisis on Infinite Earths." Even when Barry was restored to life, Wally continues to operate as a speedster.

The character made his live-action debut during the second season of The CW's The Flash where he was introduced not as Iris's nephew, but as a long-lost brother she didn't know she had, as her mother had abandoned Iris and Joe because of her drug addiction and never told Joe she was pregnant. Despite this difficult backstory, Wally soon became a fixture on The Flash, though he didn't develop speedster powers until later. Wally is first shown having speedster powers in Season Three, initially during the Flashpoint timeline as a result of Barry going back in time to change the past.

When Barry puts the timeline back to right, Wally loses his speed powers. This is difficult for Wally as his then-girlfriend, Jesse Quick, had developed super speed after they were both exposed to dark matter. Wally struggles with not having speed powers and begins to have dreams stemming from Flashpoint in which he did. The villain, Alchemy, later restores Wally's powers and he suits up as Kid Flash to help protect Central City alongside Barry where he is instrumental to defeating Season Three's major villain, Savitar, and when Barry sacrifices himself to the Speed Force to save the world, Wally continues to protect Central City.

However, Barry's return this season left Wally feeling unneeded. His girlfriend also broke up with him and to deal with the disappointments in his life, Wally decided to go to Blue Valley to figure things out for himself. Wally later returned to Central City for Barry and Iris' wedding and was tapped to get his father, Joe, and Joe's girlfriend, Cecile, to safety when Nazi's from Earth-X invaded.

With the Legends in need of a new teammate and Wally needing a place to serve as a hero, Wally making the jump to the Waverider makes sense, giving the character a chance to grow as a hero and make new friends in the process.

"We loved working with Keiynan in our series premiere — the episode in which we learned that in between seasons 2 and 3 he had been fighting crime in Central City with Nick Zano's Nate Heywood. So, when his character stepped away from Flash to go on walkabout, after being dumped and feeling somewhat estranged from his family and team, we knew that Wally West would fit in perfectly on Legends," executive producer Phil Klemmer said in a statement. "After all, our show is about a collection of unlikely heroes who all began their journeys questioning who they are and where they belong — only to find those answers while traveling through time and having wacky adventures. So now, Wally West is not only back in the company of old friends from the Arrowverse, he's fighting alongside a former enemy and career arsonist Mick Rory/Dom Purcell. By the end of this season, Wally will learn that the Legends have a different definition of what it means to be a hero."

Legends of Tomorrow airs Mondays at 8/7c on The CW.