AceShowbiz -

The Flash and Arrow's funny banter is one of the things that you don't want to miss in The CW's 4-night crossover event. In a new promo for the epic crossover, Barry Allen a.k.a. the Scarlet Speedster and Oliver Queen have a little argument in the middle of a fight.

It appears that Barry asks for Oliver's help when aliens land on earth. Even Supergirl a.k.a. Kara says she can't fight these bad guys alone, so DC's Legends of Tomorrow are also on hand to save the world. Harrison Wells, Felicity Smoak and Cisco, who describes the aliens as "World War Z" zombies, will also appear on the crossover.

In "Invasion!" which is based on the 1988 comic book event miniseries, The CW's heroes team up when The Dominators, mind-controlling extraterrestrials, assemble to bring an end to the threat caused by Earth's surging population of metahumans. These superheroes will fight each other, according to EW.

The four-way crossover will begin with the November 28 episode of "Supergirl" and continue in all three hours of "Arrowverse" of the week.

Before that, "Supergirl" will air a new episode titled "The Darkest Place" on Monday, November 21 at 8/7c. According to the official synopsis, "while Guardian tries to clear his name after being accused of a murder committed by another vigilante, Supergirl heads out on a solo mission to rescue Mon-El who has been captured by CADMUS. While fighting to free Mon-El, Supergirl comes face to face with Cyborg Superman."