Special Guest Stars Stephen Amell as Oliver Queen / Green Arrow Grant Gustin as Barry Allen / The Flash Melissa Benoist as Supergirl / Kara Zor-El / Kara Danvers Emily Bett Rickards as Felicity Smoak Danielle Panabaker as Caitlin Snow David Ramsey as John Diggle Carlos Valdés as Cisco Ramon Guest Stars Christina Brucato as Lily Stein Lucia Walters as The President Donnelly Rhodes as Glasses Co Starring Jacob Richter as Younger Glasses