Girls Night Out

"Girls Night Out" is the fifth episode of the fourth season of The Flash, and the seventy-fourth episode overall. It aired on November 7, 2017.

Synopsis
Having received an ominous threat from her old boss, Amunet, Caitlin fears that her past time as Killer Frost may be back to haunt her. Felicity comes to Central City to help the girls celebrate Iris’s bachelorette party, while Cisco, Joe and the guys take Barry out for a night on the town.

Trivia

 * This is the first episode in which Barry appears only as a civilian and not as The Flash.
 * Felicity references the Incredible Hulk in comparing Killer Frost taking over Caitlin's mind.
 * This is the first episode in which Barry is drunk.
 * This is the first episode in which we see DeVoe in a place other than his secret lair/base.
 * When Ralph was trying to describe Joe's house and Cisco interrupts about the house being bitchin' references when Barry was entranced after coming out of the speed force and writing the symbols which translated into the sentence "this house is bitchin'".
 * Joe and Joanie reference Doctor Who and Jodie Whittaker when Joanie says she likes that the Doctor is about to become a woman.