Scenes had to be rewritten and rescheduled when series lead Grant Gustin contracted Covid during filming of the finale and continued testing positive for 10 days. Hunter Zolomon actor Teddy Sears was meant to have a final conversation with Gustin's Barry Allen that had to be scrapped. Gustin had to come in the Saturday after filming wrapped to conclude shooting on special effects sequences due to missing so much of principal photography.
Chester uses the exclamation "Dazzling Dwayne McDuffie!" Dwayne McDuffie was a longtime comic book and television writer often associated with DC comics and related productions. McDuffie sadly passed away in 2011 one day after his 49th birthday.
When Harrison Wells/Thawne is first shown in S.T.A.R. Labs, he's sitting in a motorized wheelchair, which is how he is originally in the series. Though Wells sitting in the wheelchair is somewhat obscured by the console at the intro, the empty wheelchair can be seen in the background when Allegra is trying to wake up Chester.
Carlos Valdes wanted to appear in the final season, but scheduling conflicts made it impossible (he was filming Up Here (2023) around the same time). "Honestly, there was no way to make it happen," he says, "which was really heartbreaking to me because I thought, if decided to step away from the show, at the very least I have to be there for the finale to round this thing out."
When Tom Cavanagh and Danielle Panabaker have their final conversation as Harrison Wells and Khione, neither is playing the same character they were when they started the series together, nor are they playing a version of their characters who've interacted before.