Keiynan Lonsdale's Wally West will guest star in three episodes of The CW's The Flash season 5. Last season, Lonsdale exited The Flash to join the cast of Legends of Tomorrow for the second half of season 3, but won't be back as a series regular for season 4. Earlier this summer, Lonsdale confirmed he has left the Arrowverse to move on to new things.
Lonsdale joined The Flash in season 2 as Joe's son, Wally. After becoming a part of the West family, Wally eventually learned of Barry's secret identity and went to great lengths to become a superhero. Wally became Kid Flash in season 3 due to the events of the "Flashpoint" story arc. Kid Flash remained an ally to Team Flash until the beginning of season 4 when he decided to leave to begin his own journey. After being recruited by Rip Hunter, Wally joined the crew of the Waverider and helped the Legends defeat the time demon, Mallus.
In an interview with Newsarama, The Flash showrunner Todd Helbing confirmed that Lonsdale will reprise his role as Wally West in three episodes of season 5, beginning with the season premiere. Helbing admits that Wally won't be around as much as fans may want, but promises a "really cool" story for the speedster.
Helbing doesn't reveal what season 5 has in store for Wally, but the season 4 finale may explain what brings Wally back, particularly if season 5 doesn't begin with an immediate time jump. Wally returned for the birth of Joe's daughter, and was one of the people watching when Jessica Parker Kennedy's mystery girl revealed herself to be Barry and Iris' time-travelling daughter from the future. If season 5 picks up where season 4 left off, fans may see how Wally and everyone else in attendance will react to the revelation.
The addition of Kennedy to the main cast once again gives the series more than one speedster, which is one of the reasons why Wally was absent in season 4. Former showrunner Andrew Kreisberg explained that having two speedsters was a problem both financially and creatively. So having three speedsters on the show full-time would most likely cause even more problems. Though Wally may not be around for long during season 5, there's still a chance he can make a guest appearance on Legends of Tomorrow, or continue to recur in future seasons of The Flash, since Lonsdale's exit wasn't a "total goodbye."