When Barry introduces Supergirl and she levitates to prove her alien nature, she also uses her heat vision to burn her family crest into the floor behind the rest of the team. No one looks at what she's doing, only looking at her, which they should as, from their positions, her heat vision would have had to cut through Professor Stein. The heat-vision effect was added in post and not originally scripted. Later in story-time, Barry has to explain Kara's heat vision to Oliver quickly in battle, which he should know from the aforementioned introduction. Complicated by that explanation being depicted twice.