Play a match with any character on the Gotham City map, Empire Theatre arena (single match or local versus with two controllers). Push your opponent in the corner and change the time in the PS4 settings. It must be 8:00 pm (20:00) according to the console time to get the trophy. Set the time to 8:00 pm manually in the console settings. After changing your console's time, switch back to the game and trigger the level transition to get the "It's Showtime" trophy.