This is the first episode where Killer Frost appears throught the entire episode instead of Caitlin.
The episode shares its title with Crisis on Infinite Earths eponymous eighth issue, which featured Barry sacrificing himself to save the multiverse.
The man who saved Esperanza was wearing the logo of the Black Hole organization, from the comics which was connected to Godspeed.
Barry's vision shows Cisco suited up as Vibe again, hinting that he'll somehow regain his powers, However, in viewing billions of potential futures, it is possible that what Barry saw was one alternate timeline/future where Cisco never gave up his powers.