- "Oh, why should the spirit of mortal be proud? Like a fast-flittering meteor, a fast-flying cloud... a flash of the lightning... a break of the wave... he passes from life to his rest in the grave."
- —Joan Williams quoting William Knox
Faced with the news of his impending death, Barry’s resiliency suffers as he struggles to fight fate. Meanwhile, Cecile’s career as a D.A. conflicts with her identity when she crosses paths with a villainous meta-human.
- The episode shares its title with Crisis on Infinite Earths eponymous eighth issue, which featured Barry sacrificing himself to save the multiverse.
- The episode itself makes use of the title in the poem read by Joan Williams in an attempt to bring Barry back to consciousness.
- Jay tells Barry that he had spent a year tracking the spread of antimatter throughout the multiverse, showcasing a map of the Earths he had discovered thus far. The map featured annotations from Jay, which ranged from the Earths that have the best vegan food and tequila, to which superheroes call which Earth home. Towards the top of the list, next to Earth-51 (his home Earth in the comics), is the name "Thaddeus Brown." Both Thaddeus and Earth-51 were previously mentioned in "Gone Rogue". In the comics, Thaddeus was the first to hold the mantle of Mister Miracle.
- This is the first episode where Killer Frost appears throughout the entire episode instead of Caitlin.
- In the recovery bed, Barry tells Joan that she should have used Lady Gaga to reawaken him. This is a reference to "", where Caitlin and Cisco played a Lady Gaga song when Barry woke up from his coma.
- The man who saved Esperanza was wearing the logo of the Black Hole organization, which in the comics was connected to Godspeed.
- Barry's vision shows Cisco suited up in his Vibe suit again, hinting that he'll somehow regain his powers.
- However, since Barry viewed billions of potential futures, it is possible that what Barry saw was one alternate timeline/future where Cisco never gave up his powers.
- Cisco calls Killer Frost a White Walker, referencing Game of Thrones.
- Barry wears the same clothing he wore in "" when he time travelled.
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