This year in the Arrowverse, each season finale of each show featured a setup for the upcoming "Crisis on Infinite Earths" crossover (Coming December 2019). I decided to show all the teasers in the same video. Enjoy!

Episodes I took the clips from (by order):
The Flash Season 5 Episode 22 "Legacy"
Supergirl Season 4 Episode 22 "The Quest for Peace"
Legends of Tomorrow Season 4 Episode 16 "Hey, World!"
Arrow Season 7 Episode 22 "You Have Saved This City"