Tonight's episode has us watching Barry struggle to find his way out of the "Speedforce" – the mystical force that granted Barry his power. Though, we saw him in that realm, we've also witnessed the events happening on Earth; the normal reality. After the recent "Particle-Accelerator" failed to grant Barry his abilities, the remnants of the event traveled across Star Labs, knocking Harry's daughter and Wally unconscious while reanimating the former villain, Girder.
This time, he's reanimated into a walking zombie, able to transform in and out of his metal form. Here's the relation to iZombie.
Spoiler on the season finale of 'iZombie'
In the last episode of season two's iZombie, Liv's boyfriend; a functioning zombie, is tested on by the company Max Rager. Things wasn't a success, which led to her discovering Drake as a full on "Super Max zombie." In the end, she had to kill him.
This lends back to him being reanimating in the Flash's universe, where Cisco's witty remark nods turns the Vertigo/DC show, iZombie. Drake dying as a full-on zombie in iZombie, only to return as one in The Flash? Both on CW. Both shows being products of DC? Yeah, it's more of a creative nod.
Though, we know that the two didn't actually cross, this subtle nod gives light to a neighboring show. CW is home to them both.
Catch The Flash next Tuesday at 8 p.m