I rewatched last week's episode just now, and I realized that Corinne Bohrer wasn't the only '90 series cast member to "appear" in it -- the late Biff Manard (Officer Murphy, partner to Bellows) appears in one of the "file photos" about Zoey Clark/Prank.
In order to confirm that, I popped in my DVD with "The Trial of the Trickster" on it, and I couldn't resist rewatching the whole episode. I was right -- the Clarx Toys logo was exactly the same, and the music cue used for Prank was a direct lift of the cue called "Prank" from Shirley Walker's score. (I trust Walker's estate will get residuals for that.) Also, the Gadzooka Bubble Gum company they referenced was another nod to the episode; Trickster and Prank used a Gadzooka truck as a getaway vehicle (spilling epoxy-laced gum to capture the Flash). The new episode also has Prank/Zoey telling Axel she wants to "paint the town red," which was something the Trickster-brainwashed Flash said in "Trial."
"The Elongated Knight Rises" did change things about the Trickster/Prank relationship, though (or rather, it went differently on Earth-1). It painted them as an inseparable Bonnie and Clyde, but in the original version, Jesse barely tolerated Prank despite her pathological devotion to him -- presaging the Joker-Harley Quinn relationship from a few years later. (Although it was more obvious to me than ever that Mark Hamill was totally doing a Frank Gorshin Riddler impression as the Trickster, not only in voice and expressions but in body language.) Although I guess the Earth-1 Trickster was kind of similar in how he abandoned Zoey and Axel and, as Zoey said, never wanted to be a part of that family.
Interesting to view the two Flashes back-to-back like that. The old show had much cruder speed effects (though they were cutting-edge for their day) and was much more backlot-bound (the Clarx Toys building being the same Warner Bros. backlot facade that would become the Daily Planet exterior in Lois and Clark a couple of years later), and the writing and acting were broader (and the acting was honestly not very good in some cases, notably John Wesley Shipp and Joyce Hyser). Even at its wackiest, the modern show feels more naturalistic and emotionally grounded. Of course, the '90 show started out trying to be dark and serious like the Tim Burton Batman movies it was emulating, but by "Trial" as the season finale, it had become full-on, nearly Batman '66-level camp.